Underwater

Swimming

[link href="http://paizo.com/pathfinderRPG/prd/skills/swim.html#_swim"]PCB Swim Skill[/link]

Roll a Swim check once per round while you are in the water. Success means you may swim at up to half your speed (as a full-round action) or at a quarter of your speed (as a move action). If you fail by 4 or less, you make no progress. If you fail by 5 or more, you go underwater.

A character with Swim speeds can swim, hustle, or 'run' per normal rules.

Alternately, the PC can be towed by another person using the Encumbrance Rules for Dragging.

Water Dangers

==Water Dangers== (Pathfinder Core Book)

Water Dangers Any character can wade in relatively calm water that isn't over his head, no check required. Similarly, swimming in calm water only requires Swim skill checks with a DC of 10. Trained swimmers can just take 10. Remember, however, that armor or heavy gear makes any attempt at swimming much more difficult (see the Swim skill description).

By contrast, fast-moving water is much more dangerous. Characters must make a successful DC 15 Swim check or a DC 15 Strength check to avoid going under. On a failed check, the character takes 1d3 points of nonlethal damage per round (1d6 points of lethal damage if flowing over rocks and cascades).

Very deep water is not only generally pitch black, posing a navigational hazard, but worse, deals water pressure damage of 1d6 points per minute for every 100 feet the character is below the surface. A successful Fortitude save (DC 15, +1 for each previous check) means the diver takes no damage in that minute. Very cold water deals 1d6 points of nonlethal damage from hypothermia per minute of exposure.

Drowning Any character can hold her breath for a number of rounds equal to twice her Constitution score. If a character takes a standard or full-round action, the remaining duration that the character can hold her breath is reduced by 1 round. After this period of time, the character must make a DC 10 Constitution check every round in order to continue holding her breath. Each round, the DC increases by 1.

When the character finally fails her Constitution check, she begins to drown. In the first round, she falls unconscious (0 hp). In the following round, she drops to –1 hit points and is dying. In the third round, she drowns.

Unconscious characters must begin making Constitution checks immediately upon being submerged (or upon becoming unconscious if the character was conscious when submerged). Once she fails one of these checks, she immediately drops to –1 (or loses 1 additional hit point, if her total is below –1). On the following round, she drowns.

It is possible to drown in substances other than water, such as sand, quicksand, fine dust, and silos full of grain.

Cold

Deep water and cold water bring additional dangers of cold weather exposure.

The Plactik Ocean is a [b]Cold Weather[/b] environment at 50 feet depth or below. Oceanic localized conditions may cause a change in this temperature as determined by the DM. Local conditions for smaller bodies of water are determined by the Board DM.

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(PCB - Cold Dangers) Cold and exposure deal nonlethal damage to the victim. A character cannot recover from the damage dealt by a cold environment until she gets out of the cold and warms up again. Once a character has taken an amount of nonlethal damage equal to her total hit points, any further damage from a cold environment is lethal damage.

An unprotected character in cold weather (below 40° F)must make a Fortitude save each hour (DC 15, +1 per previous check) or take 1d6 points of nonlethal damage. A character who has the Survival skill may receive a bonus on this saving throw and might be able to apply this bonus to other characters as well (see the skill description).

In conditions of severe cold or exposure (below 0° F), an unprotected character must make a Fortitude save once every 10 minutes (DC 15, +1 per previous check), taking 1d6 points of nonlethal damage on each failed save. A character who has the Survival skill may receive a bonus on this saving throw and might be able to apply this bonus to other characters as well. Characters wearing a cold weather outfit only need check once per hour for cold and exposure damage.

A character who takes any nonlethal damage from cold or exposure is beset by frostbite or hypothermia (treat her as fatigued). These penalties end when the character recovers the nonlethal damage she took from the cold and exposure.

==Aquatic Terrain (Pathfinder Core Book)

http://paizo.com/pathfinderRPG/prd/environment.html#aquatic-terrain-103 = PCB Aquatic Terrain

This link covers:

-Flowing Water

-Swept Away

-Non-Flowing Water

-Stealth and Detection Underwater

-Invisibility

-Underwater Combat

-Ranged Attacks Underwater

-Attacks from Land

-Fire Underwater

-Spellcasting Underwater

-Floods