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.

Perception

• 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

• 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.

Swimming

• 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″)

Combat

• 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

Magic

• Spells can be cast underwater (subject to spell restrictions under water).
• Water Breathing potion: 6 turns + d10 rounds
• Polymorph: 4 turns + d4 turns

Moving Water

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.

Last updated: 161201…200722

Almost everything in AD&D that moves has a defined movement rate based on combat rounds. But things move for longer than combat, and further distances than in practical units of 60 feet. The Dungeon Masters Guide (DMG) provides details for large scale movement, and the Wilderness Survival Guide (WSG) provides yet more. Yet movement still all breaks down in combat scale movement. In that context, long-range movement doesn’t readily take into account variables like fatigue, terrain and flight, without a lot of painstaking math each time I needed to figure it out.

Fortunately, painstaking math is one of my specialties. Skip to the end for the detailed summary if you don’t want to read through the math.

Basics

The Players Handbook (PHB) defines base movement as 1″ = 1 mile/half-day (where half-day is defined as 8 hours), or 8″ = 1 mph, 12″ = 1.5 mph. The Wilderness Survival Guide (WSG) further defines that base movement is unencumbered across rugged terrain. So a 12″ movement is 12 miles/half-day on foot on rugged terrain, or 15 miles/half-day on foot on normal terrain (1.875 mph). An unencumbered character can move an accelerated 18″ on normal terrain ( 2.25 mph) but risking fatigue, so won’t be able to keep that up all day, at best 6 + 5 + 4 + 3 + 2 + 1 (+1, +1, +1, …) turns, or 21 turns (3.5 hours), so not faster than not accelerated over the course of a day.

WSG further defines movement on land on foot at 3/4 speed for the second half-day, or 21 miles in 16 hours @ 12″ unencumbered over rugged terrain (1.3125 mph), or max 26.25 miles in 16 hours over normal terrain (1.64 mph), min move on very rugged terrain of 8″ + 6″ = 14 miles in a day (0.875 mph).

An encumbered human would be 9″ movement, or 9 miles / half day on rugged terrain, or 12 miles / half day on normal terrain (1.5 mph).

Mounted Movement

For light horses, movement is 24″ unencumbered on normal terrain (where 1″ = 1 mile/half-day). A horse can be forced to move continually (without risking fatigue) for one-half its current movement rate (max of 12 hours). In a day a horse can go 24″ for 8 hours + 24″ for 4 hours, or a total of 36 miles in a 12-hour day (3 mph), 18 miles/day on rugged terrain (12″ for 6 hours + 12″ for 3 hours @ 1.5 mph) or on very rugged terrain (6″ for 3 hours + 6″ for 1.5 hours = 9 miles for 4.5 hours @ .75 mph). Fatigue for horses occurs when moving longer than allowed, a cumulative chance of 20% (normal), 35% (rugged), 50% (very rugged), checked every hour.

Note: WSG differs from the DMG, which lists mounted movement as 60 miles/day (normal), 25 miles/day (rugged), and 5 miles/day (very rugged). The assumption here is that they’re both vaguely correct, where the doubled distance is possible with fresh mounts.

WSG indicates that encumbered horses must rest for one turn after every six turns traveled to avoid fatigue, so the same travel takes longer to accomplish. This adds: 2 hours on normal terrain, 1.5 hours on rugged terrain, and 1 hour on very rugged terrain.

Movement for fatigued mounts is half, but they can burst move for 1 round per turn. A pony may be specially-bred for movement in mountainous terrain, but WSG does not define how much faster it can go.

A horse can travel at a gallop for about 10 miles before tiring, so fresh mounts would be required every hour.

Vehicular Movement

Since things wouldn’t be complete without vehicular land movement, a horse-drawn cart moves but 8 miles per half-day, and while WSG doesn’t call it out, the second half-day is likely limited to horse movement of only 4 hours, so you end up with 12 miles total movement in 12 hours, or 12 miles/day (1.0 mph) over normal terrain. Note “normal” in this context involves flat, featureless ground or roadway, otherwise the terrain is one scale worse.

Swimming

Unencumbered human characters swim on the surface at 4″ (3″ for humanoids). Their swimming endurance is calculated at (Level + Constitution score) * 2 [because they are unencumbered] turns. Assuming no current (pro or con), that means a 0-level character with a 11 Con could swim for 22 turns (3 2/3 hours), a 8th level character with a 16 Con could swim at 4″ for 48 turns (8 hours), or .5 mph. Quite fast then is the Cloak of the Manta (18″ with no duration, or 2.25 mph). The Ring of Swimming (21″ for 4 hours, then requiring 1 hour of floating) better still, at 7 hours of swimming for 1 hour of rest in 8 hours (2.3 mph), or 9 hours of swimming with 3 hours of rest in 12 hours (1.97 mph)

Nautical Movement

Ship speeds are given in mph instead of scale inches, so we have to convert the other way to get all the information. The small merchant ship (DMG) goes 5 mph at normal sail. Treating the sea like uniform terrain (much like magical flight), 3″ = 1 mph, that means 5 mph = 15″, and 7 mph (full sail) = 21″. A normal sail is 40 miles/half-day. On reference the DMG indicates the same ship goes 50-60 miles, so while WSG defines ship movement as the standard 8 hour half-day, the DMG indicates that ships can effectively move 12 hours/day (making the rate match the DMG distance of 60 miles).

Add the small barge from the DMG to correlate the DMG with WSG. The small barge is 2 mph, or 6″, which, assuming no terrain similar to flying, makes it 16 miles in 8 hours—a direct match between WG and DMG—three cheers for consistency.

A rowboat (john boat / jolly boat) goes 1 mph (2 mph under maximum oar), or 6″ (12″ under maximum oar).

A call out to the Dragon article which discusses that in AD&D, small ships are faster, yet in reality larger ships go faster, so all ship movements should really be reversed for size (large in a size class goes fastest, small slowest).

Mounted Flight

Flying creatures’ movement ranges from 12″ to 48″. WSG doesn’t discuss “Terrain” (flying after all), and references the movement to be in miles/half-day (comparable to someone on foot), so 24″ = 24 miles in a half-day (3 mph, 6 mph for 48″). The DMG is (mostly) consistent with that, except that flying mounts can never fly more than 9 hours/day (flying being a lot of work after all), as they must rest 1 hour for every 3 they fly, so assuming that includes risk of fatigue (which we’re not including here), 24″ movement is 24 miles/day, regardless of terrain!  (I’ll bet some odd things might happen if I worked through the Stamina modifiers, but we’ll skip that for now, as scale ” converts directly to miles).

A pegasus at 48″ flies 6 mph, but can do so for only 9 hours, only 54 miles / 12-hour day. A bird of prey flies at 33″, but presumably can also do so for only 9 hours / day, or 3.67 mph.

If a mount is carrying more than a normal load, its safe flying time is reduced by one turn or one-third of its normal stamina rating in turns, whichever is greater. Creatures burdened not only fly slower, but can’t fly as far.

Magical Flight

Both normal “foot” movement, and “flight” movement assume regular stopping to rest for each hour to avoid fatigue. Those on foot rest two turns after every four. Land mounts don’t stop to rest. Flyers rest periods vary wildly. For multi-day movement AD&D says nothing, but OD&D says that a human must rest one day out of every six. Because there are different rest rates, mid-term equivalent movement might not be the same—on the first turn on rugged terrain, a Fly spell moving 12″ goes the same distance as pedestrian at 12″, but the pedestrian moves their full movement in four turns, where the Fly takes six turns. That movement disparity for rest increases on normal terrain.

The Fly spell is 12″, but when compared to foot traffic there is no terrain consideration, and compared to mounted flight, there’s no need to rest (stamina in flyers is somewhere between 2:1 and 5:1), lending itself to another terrain type—air when flying magically! No need to rest (or even turn) has its benefits. The DMG provides insight on magical flight, as a magic broom moving at 30″ would go 10 mph (80 miles in a half-day)—every 3″ = 1 mph when magically flying. To convert the pedestrian’s rate to that, flying movement would be 3× that movement on rugged terrain, so each 1″ = 3 mph. As flying this way takes a certain amount of concentration, consider that it would also be limited to 12-hour days.

The Fly spell would then be 12″, 36 miles in a half-day of 8 hours, and 48 miles in 12 hours, or 4 mph. A magic carpet at 42″ would be 112 miles in a half-day, or 168 miles in 12 hours, at 14 mph.

A 12th level mage can memorize up to 5 Fly spells, which would translate on average to 102 turns, or 17 hours of movement (or 11 hours of safe movement with no risk of spell failure). A mage would need 6 hours of rest, + 5 × .75 turns, or 9.75 hours /day to rememorize that Fly ability, which means that 11 hours/day is repeatable (if exhausting), but they can’t actually get the full distance under their own power until level 15!

Movement Extremes

The Barbarian is assumed to have a movement of 15″ (which would be on rugged terrain), so 18.75 miles + 14 miles, or 32.75 miles/day (2 mph) on normal terrain. Barbarians with Running have the ability to run at TWICE the normal movement rate for 3 days, so 65.5 miles/day for 3 days (4 mph).

Lvl 12 monks move at 26″, or 32.5 miles/half-day, or 57 miles/day, for 3.5 mph.

Quicklings move at 96″ (presumably also a baseline of rugged terrain) and thus 120″ on normal terrain. A half-day therefore takes them 120 miles on normal terrain, and two half-days 210 miles (168 miles on rugged terrain)—13.125 mph (10.5 mph on rugged terrain).

The Cloud Trapeze spell (Wu Jen 8) permits the caster to move at 10 miles/turn, or 600 mph.

Phantom Steed at 14th Level (flight) moves at 56″, so 18.67 mph.

Shadow Walk permits movement at 7 leagues (21 miles) / turn, or 126 mph.

In groups > 100, the movement rate decreases 1 mile/day (.125 mph) for each 100 (to not decrease overall movement by more than 50%)

Validation comparing large-scale and small-scale movement

On “normal” terrain, a character moves at 15″/ round. So does that scale? Well, that’s 150 yards/minute outdoors, moving 4 turns out of 6. During an 8-hour half-day, the character moves 5.33333 hours, or 32 turns, or 320 minutes. 320 *150 = 48,000 yards, or 27 miles in a half-day. Off by roughly a factor of 2; the only way to adjust would be moving but 2 turns out of 6 over an 8 hour day; almost everything lines up then, but doesn’t make sense.

Looking at alternatives, if you toss out the yards math (which I always hated anyway), and call it 150 ft/minute, then it’s 9.1 miles (150*320/5280) in a half-day instead of 15 miles. Closer but not enough. What if you assume that 12″ is actually the movement on normal terrain? At 120 ft/minute, resting 4 out of 6 turns, gives your 7.3 miles /day.

But if it’s 120′ / round, and 8-hour day, and constant movement averaged over time? 10.9 miles/half-day, darned close to the 1″ = 1 mile math. Just throw out and “inches = yards” outdoors, and the WSG “rest 4 turns out of 6” for those on foot and things actually line up. Also helps to resolve the disparity between Fly and foot on the short-term.

So who wins? In 12 hours, calculating in rest:

* Groups > 100 move 1 mile less / day

Final note: a reminder that all of the on-foot, sailing, and flying movement can be considerably faster based on conditions (wind) or willingness to push endurance; and averages above are on a daily basis, on a half-day basis most things are faster.