“The mysteries of the oceans are as deep and dark as the waters themselves. These are the primeval birthing pits of the world, where creatures as ancient as the world’s heart still swim in hidden trenches. Vast oceans sprawl beneath the ground, with never a ray of sunlight breaking their murky waters. Civilizations formed and grew, suffered and died, and the bones of their cities still lie on the ocean floors.
"The oceans guard their secrets well. Those finned and gilled beings who call the waters home think they understand it, but the ocean hides its truths even from them. Serpents that can swallow ships whole, tentacled monstrosities with ancient memories, and behemoths that rise only at the bidding of the gods inhabit the deeps.
"The most fervent refuse to be deterred by the oceans’ dangers. Seekers in pursuit of truly ancient knowledge and the very deepest secrets begin and end their search in the water, for that is where our world itself began and shall someday end.”
— Eldrinex the Distant, oceanologist and explorer
FAQ - Quick Refrence Guide to Water in Pathfinder
When do I need to make a Swim check while in the water?
I have freedom of movement / free swim!
I don't want to make swim checks! Congratulations, you don't.
I have a swim speed!
I'm stuck! (pinned by a rock, leg wrapped in seaweed, etc.) The Swim DC is set by the obstacle (default 20-30).
I'm being swept away! (Rapids, powerful current, etc.) Attempt a DC20 Swim Check to resist, and you may take a 10.
I'm fighting rapid buoyancy! (Magic, Heavy Armor, Underwater Gyser, etc.) Attempt a DC Swim Check to resist, and you may take a 10.
I've been knocked off balance! The Swim DC is equal to the previously failed Swim check OR equal to the Combat Maneuver that knocked you off balance (Trip, Bull Rush, etc.), and you may take a 10.
I've been swimming for an hour! Attempt a DC20 Swim Check or you take 1d6 points of nonlethal damage and fatigue.
I don't have any of the above...
I want to move. The Swim DC is 10-20 depending on conditions.
I don't want to move, but I want to resist my buoyancy. As a free action, attempt a Swim Check with the same DC as attempting to move, or a DC20 if you are rapidly rising/ sinking.
I'm stuck or being swept away! (pinned by a rock, powerful current) Attempt a Swim Check (default DC is 20-30).
I've been knocked off balance! The Swim DC is equal to the previously failed Swim check OR equal to the Combat Maneuver that knocked you off balance (Trip, Bull Rush, etc.).
I've been swimming for an hour! Attempt a DC20 Swim Check or you take 1d6 points of nonlethal damage and fatigue.
How does holding my breath work?
How long can I hold it normally?
1 round per 2x CON score.
What reduces how long I can hold it?
Standard Actions - Every standard action reduces your remaining breath by 1 round.
Verbal Components - Every spell/ability with a verbal component reduces your remaining breath by 3 rounds (must have at least 3 rounds left), or by 1 round if it has a casting time of swift or immediate (must have at least 1 round).
Breath Weapons - Using a breath weapon uses up 5 rounds (must have at least 5 rounds left).
Talking - A Short speech (5 sylables or less) reduces your remaining breath by 3 rounds (must have at least 3 rounds left).
Screaming - Screaming reduces remaining breath by half or by 10 rounds, whichever is greater (must have at least 5 rounds left).
Cold Water Gasp - A warm-blooded creature who falls or is dropped into cold water (uncontrolled) and plunges at least 10 feet gasps in cold water and must immediately begin making fortitude saves as though they ran out of air.
Being Strangled - Spells or abilities that force you to hold your breath while already holding your breath (like a chokehold) doubles your air expenditure each round.
Stolen Air - Spells or abilities that steal your breath either list the amount or temporarily suspend all remaining rounds of air (like steal breath).
Knocked Unconcious - Being knocked unconcious removes all remaining rounds of air.
What happens when I run out of air?
Check - If you cannot breath at the start of your turn, you must make a Con check (not Fort) with a DC of 10 + 1 for each previous check attempted.
Spells - You cannot speak or use spells or abilities with verbal components.
Actions - You cannot attempt full-round actions (but you may still use both a move and a standard action, unless otherwise prevented).
Failure - If you fail your Con check before getting more air, you begin drowning.
I started drowning. What does that mean?
Step 1: Once you fail your Con check, you begin drowning and fall unconcious. If you were already unconcious, immediate skip to Step 2.
Step 2: On the start of your next turn (unless already unconcious), you begin dying and are brought to -1 hp regardless of how much health you had. If you were already at -1 or less, you take 1 point of damage (this damage counts as failing to stabilize).
Step 3: On the start of your next turn, you drown and die.
I was revived underwater, how many rounds of air do I have left?
Unconcious - If you fell unconcious while underwater while needing to hold your breath, you have 0 rounds remaining and you must immediately begin making Con checks to prevent drowning.
Drowning - If you were unconcious and had already failed your Con check and started drowning and you still cannot breathe, you remain unconcious and continue drowning normally (you are on the same step).
Breath of Life - If you were revived via breath of life, you have 0 rounds remaining and must immediately begin making Con checks to prevent drowning. If you had already failed a Con check and begun drowning, the DC is the same as your previous DC + 1.
Tell me about Buoyancy and Currents...
How does Buoyancy work?
Why does it matter? Buoyancy determines how much you float or sink in the water when you fail (or don't attempt a needed) a swim check, whether you can walk underwater on the sea floor, and how easy or hard it is to swim up or down.
What action is it to resist my bouyancy? Attempting to resist your Bouyancy is a free action at the start of your turn (or done as part of a move action), with the same Swim DC as attempting to move.
Neutral Buoyancy - If you have neutral buoyancy, you do not float or sink relative to wheree you are in the water, and you don't need to attempt a swim check to resist your buoyancy.
Rising/ Sinking - If you have rising or sinking buoyancy and fail a swim check (or don't resist), at the start of your turn, you are moved in the direction of your buoyancy. This movement knocks you off-balance and provokes attacks of opportunity. You move 10 feet on the first round, 20 feet on the second round, and 30 feet every round after.
Swift Buoyancy - If you have swiftly rising or sinking buoyancy, you must attempt a DC20 swim check at the start of your turn, or you are moved in the direction of your buoyancy 30 feet. This movement knocks you off-balance and provokes attacks of opportunity. If swiftly rising and already at the surface, you are not off-balance and may choose to stay at the surface without making any swim checks. If swiftly sinking and on a stable surface, you are not off-balance and may choose to stand on the bottom or move normally as though in difficult terrain.
Changing Buoyancy - If your buoyancy changes while being moved by your buoyancy, your buoyancy speed changes at a rate of 10 feet per round. If your buoyancy changes to swiftly rising/sinking, your buoyancy speed changes immediately.
Moving vs Buoyancy - If moving against your buoyancy (and its not nuetral), you are treated as though you are moving through difficult terrain and your speed is halved (like going upstairs). If moving with your buoyancy, you may choose to move your buoyancy speed at the start of your turn (provoking normally) before attempting your swim check to move, effectively adding your buoyancy to your total movement.
What is my Natural Buoyancy?
Water Subtype - If you have the water subtype, your buoyancy is always neutral (even if affected by magic or items).
Aquatic Subtype - If you have the aquatic subtype, you may change your buoyancy to neutral as a free action at the start of your turn (unless your buoyancy is swiftly rising/ sinking). If your buoyancy is already neutral, you may change it to rising or sinking as a move action.
Air Subtype - If you have the air subtype, your buoyancy is swiftly rising if your in a light load, rising if your in a medium load, and sinking if your in a heavy load.
Air Breathers - If you are a creature that needs to breath (like humanoids), your buoyancy is sinking if in a light, and swiftly sinking if in a medium or heavy load or wearing heavy armor.
Non Breathers - If you are a creature that does not need to breath (like constructs), your buoyancy is sinking if in a light load, and swiftly sinking if in a medium or heavy load or wearing medium or heavy armor.
What can change my Buoyancy?
Water Subtype - nothing. The only way for a creture with the water subtype to not have neutral buoyancy is for it to change its subtype (such as via a polymorph effect)
Aquatic Subtype - If you are not swiftly rising/ sinking, you can adjust your buoyancy to neutral at the start of your turn as a free action. If your bouyancy is neutral at the start of your turn, you may change it to rising or sinking as a move action.
Magic - Certain spells and abilities (like aquakinesis or extreme buoyancy) can change a creatures buoyancy.
Equipment - Certain items can be sued to adjust your buoyancy, such as air tanks and lead anchors. The magnitude of their efefct depends on your Natural Buoyancy.
Load - Picking up or dropping items to change your load can adjust your buoyancy.
How is this different from currents?
Why does it matter? Like Buoyancy, a current can move you in the water. However, a current is an outside force and may move you in any direction.
Moving Water - Any water with a current at any speed is considered moving water. Even the ocean is considered still water in abscence of a current. A current moves a person 5 feet per round for every 2 mph.
Resist Currents - Just like Bouyancy, you can resist the current as the same free action as resisting your buoyancy at the start of your turn, or as part of a move (typical DC 10-20).
Swept Away - If you fail (or choose not) to resist the current, you are moved by the current in the currents direction according to its speed. Unlike Buoyancy, this does not speed up or slow down. This movement knocks you off-balance and provokes attacks of opportunity from creatures not being swept away.
Moving vs Currents - Moving against the current counts as difficult terrain and your speed is halved (like going upstairs). If moving with the current, you may choose to be swept away at the start of your turn (provoking normally) before attempting your swim check to move, effectively adding the currents speed to your total movement.
How far can I move underwater?
I have a swim speed!
You may move up to your swim speed as a move action without making a swim check (except for extreme circumstances)
You may choose to move one quarter a different speed if you like, but you gain none of the benefits of your swim speed on that movement (including your +8 bonus on swim checks).
I have freedom of movement / free swim!
You automatically succeed on all swim checks and may choose to ignore buoyancy.
You still move one quarter your speed as a move action.
You may move your full fly speed as a move action (freedom of movement only, not free swim).
I can ignore difficult terrain!
You may move one quarter your chosen speed with a successful swim check (DC 10-20) as a move action.
You may move against your buoyancy or against the current without further reducing your speed.
You may walk along the bottom at full speed as a move action if you have a swiftly sinking buoyancy.
I have fly, burrow, fast movement, normal movement, etc.
You may move one quarter your land, fly, or burrow speed with a successful swim check (DC 10-20) as a move action, or one half as a double move.
You may move half your land or climb speed as a move action if walking/ climbing along the seafloor or another stable surface, as though moving in difficult terrain. This usually requires a swiftly sinking buoyancy.
I have non-neutral buoyancy, but I'm not being dragged.
You must attempt a swim check each round as a free action at the start of your turn to maintain your depth, or as part of your move action to move.
If you fail your swim check, you move in the direction of your buoyancy. This knocks you off-balance and the movement provokes attacks of opportunity as normal.
You may attempt to move normally with one of your movement speeds, but moving against your buoyancy counts as difficult terrain.
You may allow yourself to be dragged by your buoyancy as a free action at the start of your turn. This knocks you off-balance and the movement provokes attacks of opportunity as normal.
I am or I want to be dragged by my buoyancy or the current.
You may allow yourself to be dragged by your buoyancy or the current as a free action at the start of your turn. This knocks you off-balance and the movement provokes attacks of opportunity as normal.
You may attempt to not be dragged by your buoyancy or the current as a move action at the start of your turn (Dc 10-20). A success means you stop moving through the water and are no longer off-balance. You may only attempt this action once each turn.
If swiftly rising and at the surface, you are no longer off balance and may act normally.
If swiftly sinking and on a stable surface, you are no longer off balance, may act normally, and may walk at half speed (as though on difficult terrain), burrow normally, or climb against the ground at full (climb) speed.
How do water enviornments affect...
...fighting at the surface?
Surface Tension - Surface tension is real in pathfinder, which dictates how attacks, spells, and extradimensional spaces function underwater. Any time the two parties fighting each other are fighting through surface tension (such as one party being on land while the other is underwter, or the parties being seperated by oil etc.), these rules apply.
Total Cover - Creatures completely seperated by surface tension have total cover from one anothers attacks (including spells).
Partial Cover - Creatures not completely seperated by surface tension, but more than half of them is (such as submerged chest-deep in water) gain improved cover. Creatures less than half seperated but still seperated gain regular cover (such as wading through waist-high water). Creatures still mildly seperated gain partial cover (such as walking through water just deep enoguh to still be difficult terrain, but not stepping in a puddle).
Exception to Cover - Creatures that are both in the same body of liquid at one end of the surface tension, or who are both disrupting the same surface tension (such as both wading through the same water) do not have cover from each other. Spellcasters must choose which side of the surface tension (such as above or below the water line) is affected by their spell, it still cannot penetrate surface tension.
Piercing Weapons - Attacks that deal piercing damage can ignore the cover benefit provided by surface tension, but they take a -2 penalty on attack rolls to do so.
...concealment and detection?
Maximum Visibility - In clear water, maximum visibility is typically 4d8x10 feet (40 - 320). In murky water, maximum visibility is typically 1d8x10 feet (10 - 80). In open water, it is difficult to gain cover or concealment for stealth without swiming away from your target at least the distance of maximum visibility.
Visual Perception - All visual perception checks are made at a -2 in clear water, and between -2 and -8 in murky water (all flowing water is at least somewhat murky). In addition, cretures without the amphibious special quality, aquatic subtype, or water subtype take a -4 on visual perception checks and risk eye injury if they are not wearing some form of protective goggles.
Audible perception - While sound travels farther and faster underwater, the benefits are usually mitigated by ambient noise. In situations with particularly little ambient noise (such as no wildlife or in a sealed tank), audible perception checks gain a +2.
Scent - Creatures with keen scent, like sharks, can track blood trails from up to a mile away, making it easier to track wounded targets underwater. Regular scent works normally underwater ofr aquatic creatures, but is more tuned for detecting things at long distance. Land-based creatures typically cannot use scent underwater.
Tremorsense - Aquatic tremorsense detects disturbances in the water and functions as long as both creatures are touching the same body of water. Regular tremorsense works normally so long as both creatures are touching the same solid surface.
Tracking - Without keen scent, it is nearly impossible to track creatures underwater unless they are moving along the bottom or through something that leaves signs (like a coral reef). Even in such exceptional circumstances, water quickly washes away signs of passage, increasing the DC to track in such situations by 1 for every 10 minutes in an area without a current, and by 1 for every minute in an area with a current.
...temperature?
Why does it matter? Immersion in water causes hypothermia more easily, and have a different temperature range from the surface for what is considered cold.
Temperature range - 80* and above are generally considered safe. 60*-80* is the same as cold weather, and a creature must pass a fortitude save each hour or take 1d6 points of nonlethal cold damage. 40*-60* is treated as severe cold, requiring a save every 10 minutes or dealing 1d6 nonlethal cold damage. 32*-40* is extreme cold and deals 1d6 lethal cold damage each minute. Liquid water below 32* deals 2d6 cold damage per minute.
Overheating - Heat danagers are rare in the water except in the precense of hydrothermal vents, as even the most extreme temperatures tend to cap around 104*.
Protection - Endure elements protects its target from water as cold as 32* (as opposed to -50* in air), which is usually enough protection. Sea creatures are generally adapted to the water temperature of their habitat.
...dealing with pressure?
Air, Aquatic, and Water Subtype - Creatures with the air subtype can adapt to pressure normally, but they treat the surface as their native zone, adapting to pressure all at once when returning to the surface from underwater. Creatures with the aquatic subtype are native to one oceanic zone (for most aquatic creatures, especially ones can also walk on the surface, that is usually the sunlight zone). Creatures with the water subtype are always considered native to all oceanic zones and cannot take damage from pressure.
Surface Dwellers - Creatures not native to underwater enviornments treat the 0-100 feet underwater as their native pressure range.
Outside Native Zone - Creatures outside of their native zone must succeed at a fortitude (DC15 + 1 per minute after the first) save every minute or take 1d6 points of damage, plus 1d6 points of damage for every 100 feet beyond the first. Example: Dave the land dweller (native range 0-100 feet) is 220 feet below the surface, and has been below his native zone for 3 rounds. This round, he must make a DC18 Fortitute save or take 2d6 damage
Adapting to Pressure - Creatures outside their native zone adapt to pressure after making 5 fortitude saves (does not need to be consecutive), at which point their native zone shifts by 100 feet. Example: Dave the land dweller (native range 0-100) is 220 feet below the surface. After making 5 Fortitufde saves, his adapted native range is 100-200 feet. After making 5 more saves, his adapted native range is 200-300 feet an he no longer needs to attempt fortitude saves, though he will experience pressure hazards when he ascends back to the surface.
Teleportation - Creatures instantly transported to a depth outside their native zone immediately being making saves as normal and may be in danger is the discrepancy in depth is vast. Aquatic creatures instantly transported back to their native zone after being adapting to being outside it take damage and make saves normally, but adapt completely to their native zone after making 5 fortitude saves.
Dealing with Pressure - The easiest and safest way to deal with pressure is to adjust depths gradually. Alternatively, spells like freedom of movement, life bubble, and pressure adaptation can prevent or overcome pressure damage.
...equipment?
Evironment - Salt water is incredibly harsh, and few materials can remain submerged for oong without disintegrating or corroding. Leather, paper, wood, and textiles disintegrate quickly underwater and become worse than useless, often hampering movement, while metals rust and corrode away. A great deal of sensitive equipment also becomes permanently destroyed underwater, as the preassure breaks through formerly sealed enviornments and particles and detritus sabatoge working parts.
Other Mundane - Unprotected items (or magical items that have been submerged for a long time) vulnerable to salt water take 1d6 points of damage from the salt water every day which bypasses hardness. If the item had the fragile quality or a hardness of 0, it is always destroyed. Sensitive equipment (such as a compass) and items with the fragile quality is similarly destroyed if it takes any damage from preassure. Items submerged for 1 hour or longer underwater that isn't subsequently cleaned that day (such as washed if its clothing) take damage as if it was submerged for 1 day.
Magic - Most magical equipment is protected from basic water exposure and can usually weather prolonged exposure to salt water. As a general rule, Magical equipment can survive at least 1 day per 100gp in value before needing to make fortitude saves, and each DC10 fortitude save protects the item for one additional week. Magic that protects the caster from the effects of water (such as endure elements) also protect their gear. Items with a +3 enhancement or with any energy resistance or endure elements property are completely immune to salt water. Metals immune to rust are likewise immune to salt water. Items protected from time (such as via an ungent of timelessness) are affected by water much more slowly.
Special Materials - Most alchemically treated items have the same protection as magic items underwater. Adamantine (and other skymetals), Blackwood, Crystal, Darkwood, Dragonhide (if the dragon had a swim speed), Eel Hide, Elysian Bronze, Mithral, Spiresteel, Throneglass, and Voidglass are immune to the effects of salt water. Salt water is lethal to Greenwood and Living Steel, and any amount of damage from salt water destroys the materials ability to heal.
Primitive Materials - Many materials used underwater are considered primitive or useless above water. Bone, Coral, Obsidian, Shell, and Stone are protected from the effects of salt water, while Gold, Platinum, Silver, and other preacious metals are non-corrosive and may serve a more-than-decorative purpose. In depths of 200+ feet, water preassure helps to hold these items together, and they lose the fragile quality (if they had it).
What are Oceanic Zones?
General Info - Oceanic Zones describe the typical conditions of a specific depth, and oceanic life has typically adapted to one or more of these zone. Most surface dwelling creatures are not adapted to any of these zones.
Sunlight Zone - Depht: 0 - 660 feet. All aquatic plants that require light for photosynthesis exist here and is home to most marine mammals, aquatic humanoids, and fish familiar to most fisherfolk. Temperatures here are based on surface conditioins (from 100*-30* typically). This zone has enough light to see with normal vision during the day.
Twilight Zone - Depth: 660 - 3,300 feet. With roughly 1% of light reaching this zone, there is not enough light for photosynthesis, and creatures typically feed on falling detritus. Despite this, roughly 90% of Golarion's fish live in this zone. Creatures with low-light vision can see to a distance of around 60 feet and treat the area as dim light. Many creatures in this zone rely on darkvision or other precise senses, while others are bioluminescent. The temperatures in this zone range from about 68* at the top to around 39* at the bottom with very few variations.
Midnight Zone - Depth: 3,300 - 13,000 feet. This zone has no light whatsoever from the surface, forcing creatures to use darkvision or on visual senses if it doesnt have its own light source, though light sources tend to attract predators. The creatures of this depth are the least understood and have the largest variety, though its hard for fish to live here, being forced to scavenge on sparse amounts of falling detritus. The temperature is usually 39* throughout, and the zone typically extends to the sea floor, with the average ocean depth being two miles.
Abyssal Zone - Depth 13,000 - 20,000 feet. This rare zone is devoid of even falling detritus, preventing event simple organisms from growing or forming on the seafloor at these depths except around hydrothermal vents. Nearly empty and devoid of life, only a few leviathans, giant squid, and tentacled horrors thrive in this zone, typically resting here and hunting in higher zones when they need to feed. The temperature is a consistant 35* - 39*.
Abaddonian Zone - Depth 20,000+ feet. Some scholars, particularly among deep sea races, theorize of this zones existance in the deepest ocean trenches. With pressures over 1,000 times that of the surface, combines with low temperatures and ambient magic, these trenches could house nightmarish tableu's that hardly seem possible on the Material Plane. While some scholars have funded expeditions to the Abaddonian zone, very few have survived a trip towards its depths, and none have returned sane enough to give any accounting or what they found or if they even reached its depths.
Okay, let's talk about combat!
How does water normally affect different weapons?
Piercing - Piercing weapons typically function normally underwater, though they take a -2 on attack rolls if the wielder is off-balance or breaching surface tension. They also only deal half damage if the wielder is off-balance.
Bludgeoning or Slashing - Weapons that deal bludgeoning or slashing damage typically take a -2 on attack rolls, deal half damage, and cannot breach surface tension.
Thrown Weapons - Thrown weapons take a -2 penalty on attack rolls for every 5 feet of water, and are typically too innacurate to be effective unless thrown from directly above the target and using its buoyancy to reach it. Piercing weapons (such as spears) can be thrown from above the water in this manner taking the additional -2 on attack rolls for breaching surface tension.
Ranged Weapons - Ranged weapons not designed to be used underwater take a -2 penalty on attack rolls for every 5 feet of water. Underwater ranged weapons are designed to overcome this penalty, but typically have a reduced range. Piercing weapons (such as harpoons) can be fired from above the water at its target, taking the additional -2 on attack rolls for breaching surface tension.
Combat Maneuvers - Most combat maneuvers work normally underwater, but creatures without a swim speed take a -2 penalty on grapple combat maneuvers. Damage dealt via grapple and via attacks with the grab special ability deal full damage underwater, even if the damage is bludgeoning or piercing.
How do you cast magic underwater?
Holding Breath - Any time a creature is holding its breath (such as being underwater) and attempts to cast a spell, they must suceed at a concentration check (DC 15 + spell level) to cast a spell at all, even if it has no verbal components.
Verbal Components - Every spell/ability with a verbal component reduces your remaining breath by 3 rounds (must have at least 3 rounds left), or by 1 round if it has a casting time of swift or immediate (must have at least 1 round).
Spell Components - Mundane spell components generally work fine underwater, and aquatic-appropriate subtitutions exist for any mundane component that would be inherently impossible to use underwater.
Surface Tension - Spells cannot typically break surface tension, and creatures completely seperated from you via surface tension have total cover from your spells.
Spell Descriptors - Certain spells work differently underwater, often determined by its spell descriptors. Check the "How does water affect different types of spells and abilities?" section for more information.
What does it mean to be off-balance?
What is it? Off-balance is a special state (not technically a condition) that provides a few combat adjustments.
What does it adjust? A creature off-balance is treated as flat-footed, its piercing weapons become as ineffective in water as bludgeoning weapons, and its opponents gains a +2 on attack rolls against it.
How does it happen? Generally, any time a creature fails a swim check or allows itself to be dragged by a current or its buoyancy, it becomes knocked off-balance. It can also be inflicted on a creature who would normally be knocked prone, such as via a trip, bull-rush, or overrun combat maneuver.
How can I overcome all these penalties?
Spells - A great many spells overcome the penalties of being underwater, with freedom of movement, water breathing, endure elements, and life bubble being the most all-encompassing and generally useful.
Swim Speed - Having a swim speed overcomes a lot of the penalties of being underwater, especially if it comes with water breathing.
Class Abilities - Many class abilities, options, and archetypes bypass or override the normal effects of fighting in water.
Combat Feats - Several combat feats and stypes allow characters to live and fight underwater, with one of the most useful being aquatic combatant.
Metamagic Feats - Several metamagic feats allow casters to cast spells underwater with differet or enhanced effects, such as murky spell, steam spell, or aquatic spell.
How does water affect different types of spells and abilities?
Magical Acid
Conjuraction (creation) - These spells conjure acid to deal damage and are diluted by open water to the point where they become harmless (example, acid splash).
Evocation - These spells deal raw acid damage and are unaffected by water (example, fireball affected by Elemental Spell metamagic).
Magical Clouds and Weather
Bubble Spells - Bubble effects (such as air bubble and invisibility bubble) always work underwater and are often designed to work in enviornments where other spells of their type would not function.
Conjuration Clouds - Spells that conjure a cloud of something (like fog cloud or glitterdust) or mimic the effect of a conjuration cloud (like virulent miasma) do not function underwater unless they explicitly state otherwise.
Transmutation Clouds - Spells that turn something into a cloud (like gaseous form) and spells that mimic those effects do not function underwater.
Illusion, Enchantment, and Evocation Clouds - Illusiory or Enchanting clouds and abilities function normally in the water, as they are not creating a real substance. Evocation clouds (like aggressive thundercloud) function normally, but cannot manifest its presence and dissipate after 1 round as if dispelled.
Wind effects - Wind effects cannot manifest underwater at all.
Weather Spells - Many weather spells adjust weather conditions on land (such as sleet storm) and cannot work underwater at all. Others only adjust conditions on the surface (such as control weather) and have limited effect at depths below the surface and near zero effect below 100 feet. Illusiory effects, however, always function.
Magical Cold
Conjuration - Spells that conjure ice work normally underwater.
Cold Damage - Spells that deal cold damage (such as cone of cold) that do not conjure cold directly instead deal half cold, half piercing damage as the cold creates jagged ice shards underwater.
Magical Electricity
Ranged Touch Electricity - Spells that create electricity and deal damage at range hold their integrity enough to have normal effects underwater, except it lacks the normal visual and audible components of combusted air. Treat these spells as though they are invisible (+2 attack, target is flat-footed) the first time this type of spell is cast by that caster in combat. This effect cannot be overcome by abilities that detect only magical invisibility (such as true seeing) or rely on sound or scent to overcome invisibility (such as sonar) but can be otherwise overcome by blindsight.
Touch, Area of Effect, and Partial-Electricity spells - The electricity portion of these spells function normally.
Magical Fire
Non-magical Fire - Normal fire (including alchemist fire) does not fucntion underwater at all.
Supernatural Fire - Most supernatural fire effects do not function underwater at all.
Magical Fire - Fire spells may transform into steam with the caster succeeding at a caster level check (DC 20+ spell level) dealing the normal ammount of fire damage but without any secondary fire effects, such as igniting combustables.
Steam Spells - Spells or abilities that already create steam (such as a kineticist's steam blast) function normally underwter.
Magical Invisibility
Regular Invisibility - Invisible creatures still displace water, and only gain concealment (20% miss chance) instead of total concealemnt underwater, just like during a rain storm.
Invisibility Bubble - This specific spell hides water displacement, and works normally underwater, though it only provides concealment out or water or in a rain storm.
Magical Sonic Effects
Option 1 - A caster of a sonic spell may choose for it to funtion normally.
Option 2 - A caster of a sonic spell may choose to double the spells rage in exchange for halving the damage and reducing any spell DCs by 2.
I have an edge-case question about a specific thing...
Using Potions Underwater
Potions and extracts cannot normally be used underwater due to surface tension - It's not as much that the water dilutes the potion as much as the potion can't come out without air going in.
Potion Sponges are cheap and easy items that allow you to consume potions and extracts underwater. Also, any spell that creates a safe and breathable enviornment (like life bubble) allows you to drink potions underwater.
Extradimensional Spaces
Newly conjured extradimensional spaces use the surrounding enviornment for their atmosphere, so casting rope trick would create an extradimensional space filled with water if cast underwater. The exception to this are spells which also create an enviornment (like Mage's Magnificent Mansion).
Due to surface tension, if the entryway of an existing extradimensional space moves to a new location, it retains its original atmosphere (if it had air, it still has air that can't be let out, if it had water it still has water that can't be let out).
Extradimensional containers (like a bag of holding) are designed to maintain surface tension and only allow attended opbjects in and out (otherwise, they would rupture quickly after being overloaded). As such, a bag of holding remains filled with air underwater (unless a caster enters it and fills it with conjured water). However, if the container cannot replenish its fresh air/water supply in its new location, the air/water inside is considered stagnant and is not breathable.
Items removed from an extradimensional container while underwater are usually soaked through immediately. Should items be placed inside the container while underwater, enough water is able to breach the surface tension with the item to the generally get everything inside the bag wet, though not enough to weigh down the container. Wet items added to a bag above water tend to make many of the bags contents moist over time in the sealed enviornment. For this reason, it is often wise to keep certain items (like spellbooks) in a waterproof bag inside extradimensional containers if underwater adventuring is expected.
Freedom of Movement
Benefits and Limitations - This spell negates most of the penalties of being underwater, including dealing with pressure, making swim checks, dealing with difficult terrain (such as moving against a current), damaging equipment, and attack and damage penalties (such as using a slashing weapon). It does not, however, grant the ability to breathe underwater.
Normal Movement - Freedom of Movement allows a creature to move normally in their given enviornment. As creatures cannot walk in water, their land speed would still be 1/4 normal as they swim, they simply do not need to make checks, as it does not allow creatures to pretend water is solid enough to walk on (above or under water). It does allow a creature to walk along a stable surface (like the seafloor) underwater at full speed.
Other Forms of Movement - This spell enables creatures to travel at full speed with flight as though in air or with burrow as though underground. This spell does not allow creatures with abilities like earth glide to pretend that water is earth. It also does not allow creatures with a climb speed to pretend there are things they can climb against, just as it does not allow creatures to pretend there are things to walk on.
Breath of Life
Breath of Life may be used to rescue a drowning or drowned character, even underwater. In the event a creature drowned, they are treated as though they had taken damage equal to the ammount required to slay them for the purposes of this spell.
If a drowning creature is not healed enough to render them concious and they still cannot breathe, they continue drowning normally. If a drowned creature is not healed enough to render them concious and they still cannot breathe, they return to Step 2 of drowning, take 1 point of damage, and drown at the beginning of their turn.
If a drowning or drowned creature is healed enough to become concious and they still cannot breathe, they must immediately make a Con check at their previous DC + 1. If they fail, they resume drowning normally at Step 1.
Off-Balance Special Circumstance
Causes - Failing a swim check, getting "knocked prone" while underwater or levitating or while riding or flying without being knocked to the ground or while "swimming" on land, or allowing yourself to be moved by someone or something else in a way that provokes attacks of opportunity while flying, riding, or swimming.
Penalties - You become flat-footed, you take a -2 on atack rolls, and enemies gain a +2 on attack rolls against you.
Resolution - You spend a move action to right yourself. This requires a swim check if underwater, a ride check if mounted, a fly check is in the air, or an acrobatics check (DC10, creatures with a land speed can take a 10) if on land.
Swimming in Unusual Terrain
Water-like Terrain - This terrain include things that aren't water but are mostly water, such as: alcohol, bogs, dirty water, urine, or other viscous materials. Swimming in this terrain type uses the same rules as regular water, but water breathing creatures are exposed to anything in the water (like poisons) as if it was both ingested and inhaled, rolling against the higher DC (if varied). Creatures with the amphibious subtype gain a +4 bonus on fortitude saves against these effects.
Unusual Terrain - This terrain include things that arent mostly water but could be swum through, auch as: bile, flotsam, oil, quicksand, mucus, mud, slime, slush, and tar. Swimming in this terrain types is treated as difficult terrain, creatures with a swim speed cannot take a 10 in these enviornment, and such creatures only gain half the bonus of their swim speed on swim checks (+4 instead of +8). Creatures that can breathe water can still suffocate, but it takes twice as long.
Dangerous Terrain - This terrain includes anything that is naturally hazardous but could be (theoretically) swum through, such as: acid, burning oil or tar, crushing detritus, freezing icewater, or lava. Swimming in this terrain type is treated as difficult terrain, creatures with a swim speed cannot take a 10 and lose their, and such creatures do not gain the bonus of their swim speed on swim checks (+0 instead of +8). Many of these terrains are more readily navigated via other means.
Non-liquid-fluids - It is not normally possible to swim through these types of terrain, such as air, foam, steam, etc. However, when it is possible to swim thorugh these terrains, it is treated as difficult terrain.
