|This article is about the current version of DF.|
Swimmer is a skill used by creatures to move through tiles containing deep liquid (primarily water), and generally avoid drowning. Creatures may have a
[GAIT] creature token that defines their movement speed while swimming. For dwarves, the default values result in movement five times faster on land than in water. However, a creature's effective swimming speed can be modified by its Swimmer skill level; a legendary swimmer may be faster in water than on land.
Dwarves with dabbling (level 1) or no experience as Swimmers will start drowning immediately upon contact with deep surface water (i.e. surface water of 7/7 depth). Those of novice (level 2) level experience or greater can be in deep surface water without drowning. Any dwarf will start drowning in 7/7 water if there is more water on levels above them (e.g. they are at the bottom of a two level deep cistern, or the bottom of the ocean). A bridge (or presumably any other building that prevents access to the air above the water) will also cause non-aquatic/amphibious creatures to begin drowning in 7/7 water--this can be useful for disposing of trolls in a drowning pit.
Any conscious, uninjured, not stunned dwarf finding themselves in water of depth 4/7 or greater will try to leave if they can find a path out of around 20 tiles in length or less. If they can't find an exit within that distance, they won't move.
Novice swimmers are able to get out of deep water safely without needing a ramp or stairway, but they will start drowning if stunned. Once that happens it can be difficult to get them out, as they lose the ability to exit anywhere and behave just like an untrained or dabbling swimmer. Everyone is stunned by falling into water rather than entering it calmly, which is what normally happens when they aren't entering it of their own free will.
Adequate (level 3) swimmers do not panic and start drowning in that situation, even when attacked, so training to this level is highly recommended. Higher levels only increase speed while swimming.
Note that you can drown in magma as well, but most creatures tend to melt first.
 Learning/Teaching swimming
A dwarf in the water will gain the ability to swim very fast - sadly not fast enough to prevent death from drowning. While water with a depth of 7/7 is deadly for non-swimmers, 6/7 or less will not harm any dwarf. So you can use water from 4/7 to 6/7 safely to teach dwarves how to swim. The speed of learning is independent of the depth, but water with a depth less of than 4/7 is not deep enough to make a dwarf swim, and therefore learn anything.
Training your dwarves just requires a place of constantly or temporarily 4-6/7 water. Military orders or making rooms a meeting hall will not entice dwarves into the water, so you may need to prevent them from leaving an area (locked door, etc.) and then fill the area with the required amount of water, or dump them in from above using a retracting bridge.
Swimming, since it involves no activity, can be potentially useful to train physically handicapped dwarves, whose conditions might go away or become manageable with an attribute boost to strength, endurance, willpower etc.
A fully automated method to train idlers is to use water flowing over a 1-z drop, with a 1-wide meeting zone at the top of the ledge, and a swimming pool at the bottom. Idlers will go to the meeting zone, be swept over the side into the pool and swim to the ramp, and repeat this for as long as they are idle. The meeting zone must have a low enough rate of flow that it has unsubmerged tiles, so dwarves voluntarily move into it. This can be accomplished with tricks like restricting flow through diagonal passages (see Pressure for details). Be aware that in recent versions dwarves can now suffer injuries more easily when falling, so this method can cause serious harm when the dwarves are washed over the edge. Constructing the landing zone out of lighter materials will help prevent serious complications.
Diagram of the 'fully automated' configuration described above: .... - (pool continues as desired) ║≈≈≈≈║ - depth 4-6 swimming pool on Z-1 ║+++▲║ - dropoff / entrance ramp from above ║~~~~║ - meeting hall, depth 0-3 ╚╗%╔═╝ ║%║ - screw pump (S->N) ║.║ - limited pump source (e.g. depth ~4-per-tick tile on Z-1) ╚═╝ Not pictured: exit from the swimming pool, preferably close to the entrance ramp to minimize delays in training.
 Minecart training
With the addition of minecarts, a safe automated swimming experience can be almost guaranteed. Originally, the design involved hauling dwarves down into a pond and forcing them to swim back out. However, it was discovered that dwarves gain swimming skill while simply riding in the minecart. A simple loop track which descends 1 z-level into a pool of water then climbs back out will train your dwarves quickly and conveniently. It is advisable to ensure your pond has a uniform depth--fluid flow can interfere with the minecart, even knocking it off-track. A depth of 4/7 or 5/7 is ideal. Note that water will slow the minecart considerably; you'll want an impulse ramp after roughly 10 tiles of 4/7 water.
- Carve the tracks and add impulse ramps (shown) or rollers on level z.
- Optionally, add statues or other buildings along the tracks for your dwarves to admire (make sure to leave the corner walls intact).
- Fill the track section on layer z with 4/7 water.
- Link the pressure plate '^' to the hatch cover 'H' (this is necessary to automatically dispose of worn clothing that dwarves drop at the end of the ride).
- Set stop 1 to ride down the ramp to the east immediately/always.
- Assign a minecart to the route (wooden minecarts are recommended in case of collisions).
- Dwarves with the "Push/Haul Vehicles" labor enabled will now automatically train swimming.
 Adventure Mode
In adventurer mode, as a novice swimmer or better, by standing next to a body of water and moving carefully ( +direction) in the direction of the water (falling 1 or 2 z-levels is not an issue), you can swim about and train your skill. To get out, -move against a shoreline and select the option to move above it, or simply move toward the shore if it has ramps. You can also old onto a (non-smooth) rock wall or tree above the water's edge in order to climb out, even without any skill in climbing. It is advisable to train your skill in swimming above novice because getting stunned, winded, or tired will make you flounder and mostly likely die, even if you're just one or two tiles from a ramp. While floundering, there is a small chance to successfully move, so you might get lucky enough to make it out of the water, but don't count on it.
Swimmers can also dive and rise through the z-axis by pressing and respectively. Note that air-breathers will be unable to breathe without air in the tile above them, and without returning to the surface will eventually drown. (Sadly, there's no oxygen meter as of yet, so you'll never know when they're about to expire. Don't linger too long.)
In adventure mode, water preference can be switched between "when possible" and "necessary" by pressing.
To teach companions to swim, some patience is necessary. Enter a body of water until they follow you inside, then immediately get out. They will flounder around and attempt to get out before they drown, but as long as they make it back on land, they will gain swimming experience. Repeat until they manage to swim without drowning. Drowning itself can also be beneficial as certain attributes, notably toughness and endurance, are greatly benefited by the strain caused by the experience. Provided that the experience does not reach its fatal conclusion, the toughness of your band should reach a point where it is only be exceeded by larger or more supernatural entities.
If the temperature (press) is "freezing" or if it is "cold" and close to sundown, the water may freeze while you are swimming, which instantly kills you and leaves your frozen corpse encased in ice and a valuable find for archeologists.