Underwater Combat

SWIM  skill measures the capacity to move and float in water or liquid. The character is also trained to avoid drowning, exhaustion and hypothermia. Those with high swim skill rank are also well versed with aquatic or marine life. Typical DC for swim skill are: 

                

   9                calm water

  12               rough water

  15               stormy water

  20               quick sand              

            A character must make a swim check every turn he is swimming or travelling in water or liquid.    If successful, swim movement rate is 1/5^th normal land speed.*  If a character fails his swim skill check by five or more, he has begun to drown. 

If not standing upon a solid object, instead of applying his armor penalty to the skill check, an immersed or swimming character will subtract the Square Root of weight of all his equipment (round fractions normally) from swimming or waterborne adventure checks.

                i.e., Melinda is wearing a hauberk (20#) and she has +2 longsword (4#) and +1 oak shield (5#) in hand.  She also has a dagger (1#), two healing potions (2#), three torches (3#) and a partially full backpack (16#); therefore, total encumbrance is 51#.  If Melinda falls into deep rough water (DC =12), her Swim check penalty for armor and equipment is seven (square root of 51 = 7.14)!    She does not have time to remove her armor, so if she drops her shield, her torches, and backpack ( 5 +3 +16 = 24) and keeps all her other stuff, then penalty for encumbrance is reduced to five (SQRT of 27 ( 27= 51 -5   -3 -16).

            To attack an opponent underwater, the attacker must first make a swim check.  If and only if the swim check is successful, then the character rolls a d12**  for his to-hit roll applying normal attack modifiers  Underwater, damage is halved if using cutting or bludgeoning weapons. Damage modifiers are applied normally. Ranged weapon use is severely limited underwater; about 1/10^th range for arrows and bolts, while bullets generally travel less than ten feet! 

           

            If a character is drowning or intentionally chooses to stay below the surface, he takes damage from drowning once he is out of breath. A character can hold his breath under water in combat or other stressful activity for a number of rounds equal to five plus Con. mod. This duration is multiplied by d3+1 if and only if prepared, undisturbed and conserving energy. 

Damage for drowning is 1 hit point per round (12 seconds) without air for creatures without gills.  Certain creatures (undead, golems) either do not breath or do not require air. As long you do not go into negative hit points, drowning damage is non-lethal and heals at the rate of one hp per turn of rest.

*This value is generous for humans, dwarves, orcs and half-elves. Certain humanoid races might be faster swimmers based upon the GMz adjudication. The Olympic hero, Michael Phelps swims at speed of merely 3.6 mph  while the fastest human runner, Usain Bolt sprints at 28 mph!

 ** Roll d20 to hit an underwater opponent if and only iff attacking with a dagger or trident.