Now running a complete campaign at sea (party ghost ship and all), the questions about what the party can do in water come up all the time. As everything else in AD&D, those references are scattered across multiple books, which makes dealing with water a lot more complicated.
- 50′ fresh water, 100′ salt water.
- Light spells vision for 30′
- Infravision 1/2, 1/4 in murky water
- Ultravision halves at 100′, none at 200′
- Underwater hearing – shouts 60, communication 10′
- Endurance =(Experience Levels + CON) * turns.
- Regain 3 turns of endurance for each turn spent resting.
- 2x Swim = 10x Endurance. Tread water 2x Endurance.
Hold Breath = 1/3 CON (round up), 1/2 is surprised, 1/2 if working hard. CON checks at aggregate +2 penalty.
- Surface swimming: 4″ Human, 3″ other.
- Underwater swimming: 2/3 surface speed, rounded up
- 2″ dive/surface (doubled if not encumbered). Bonus for strength 16/17=+1″, 18=+2″, >18=+3 , +1″ when towing your way along a rope.
- Diving/Rising base speed is 2″, x2 to x3/ x2 lack/additional encumbrance.
- +1″ for first round of diving from a height for each 10′ over 5′, max of +5″.
- Diving is not cumulative with encumbrance. Natural buoyancy is .5″, or 5’/round.
- Cannot swim in non-magical armor but leather. Magic armor, can only dog paddle
- DMG, p. 55, leather/padded 5% cumulative chance/hour of drowning.
- Swimming in winds > 35 mph almost impossible, 75% likely to drown.
- Swimming at high speeds (surface only) is 2x movement, but 10x endurance normally (only 1.5x movement if normal movement would be <= speed of 0″)
- Underwater creatures will attack first w/o long weapon
- Underwater range weapons 1/10 range
- Bows useless
- Underwater crossbow 10x normal cost, 1/2 range
- Cleaving/Crushing weapons useless
- Stabbing weapons ok
- No weapon specialization
- Spells can be cast underwater (subject to spell restrictions under water).
- Water Breathing potion: 6 turns + d10 rounds
- Polymorph: 4 turns + d4 turns
Current speeds range from 1″ (gentle flow) to 6″ (raging river). A shallow river or stream in which the water is moving rapidly can harm characters by buffeting them against rocks and other protrusions in the water. A rating should be assigned of 1 to 10 to any shallow, rapidly coursing stream or river, with 1 being the most hazardous. This number represents the amount of time, in rounds, that a swimmer can traverse the water before needing to make a Swimming Proficiency Check. Failure on this check indicates that the swimmer has been thrown against the rocks, suffering d6 points of damage. A character without the Swimming proficiency is virtually helpless in similar circumstances, and will suffer d3 points of damage every round that he remains in the water. Any character can halt his movement through rough water by grabbing onto a handy protrusion. This tactic succeeds if the character makes a successful Dexterity Check; a new attempt can be made every round if desired. After catching onto something, the character must make a successful Strength Check once every two rounds to remain attached; failure indicates that they have lost his grip and is again being swept downstream.
Drowning (Dragon Magazine #107)
Drowning: When a person swims in water for an extended length of time, there is a chance that the swimmer will not be able to maintain his buoyancy; then he will drown. Consult the chart below, doubling the amount of encumbrance for mariners and treating magical ring mail, chain mail, and studded leather armor as non-magical leather, to determine at what interval a drowning check must be made. Magical leather is equal to no armor at all.
No armor or encumbrance 2 hours
Leather armor (non-magical) 1 hour
At least 50 gp enc. 1 hour
Leather and 50 gp enc. ½ hour
At least 100 gp enc. ½ hour
Leather and 100 gp enc. 1 turn
At least 150 gp enc. 1 turn
Leather and 150 + gp enc. 5 rounds
At least 200 gp enc. 5 rounds
The base chance for drowning is 25%, modified as follows:
Salt water: -10%
Calm water and/or weak current: -20%
Choppy water or moderate current: -0%
Rough water or strong current: +15%
Storm (check every turn): +50%
Treading water (0″ movement): -15%
Every previous drowning check made: +10%
Every level of mariner or sea-deity cleric: -3 %/level
Every level of sea-deity worshiper: -1 %/level
Buoying device: -5% to -50%
Note that if a drowning check is called for twice (e.g., if the swimmer is wearing leather and has 100 gp encumbrance during a storm), the character must make two drowning rolls, and the +10% factor for previous checks made applies from the first roll to the second roll.