Swimmers can move in water without drowning.
In adventurer mode, by moving carefully ( +direction) into open space above water and selecting the option to move below (such as West/Below), then you can swim about without drowning. To get out, move carefully against a shoreline and select the option to move above.
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.
It is trained by:
- Walking on an ocean wave.
- Generally getting wet.
Notable ways that it is not gained include:
- Crossing a brook.
To train swimming skill, find a pool of shallow water (preferably depth 4, which is safe) or a body of water with slopes (such as a lake). The speed of training seems to vary depending on the strength of the current; higher levels of water usually mean more current, and more pushing of your character around. Brooks count as ground tiles, you can't swim in them.
If an untrained or dabbling swimmer jumps into water, four things happen; they start drowning, they are stunned from the impact, they are forced into a prone position, and their movement speed is greatly reduced. The only way to get out of water is to use a ramp or stairway, and if neither are accessible, they're done for.
A novice swimmer is able to safely get out of water without needing a ramp or stairway, but they will panic in certain situations. Normal swimmers do not panic like novices do, so training to this level is highly recommended.
In adventure mode, water preference can be switched between "when possible" and "necessary" by pressing.
If knocked into a pond or stream in adventure mode, it is possible to escape using (alt) and a direction key to move carefully onto the shore if you are not drowning.
If a creature is surrounded by a blue status icon, they are drowning. If they cannot reach air soon, they will die. Swimmers with a normal or above rank will simply be able to swim toward the nearest air supply. Swimmers of novice or below, however, will panic when they begin to drown, and will have to get out via ramp or stairway.
The following situations will make a novice swimmer panic:
- Falling into water from a height.
- Not having air in the tile above them.
The amount of weight a creature is carrying does not make them drown faster.
 Swimming in Fortress Mode
The specifics are unknown at this point. It is assumed that dwarves with a novice rank or better will be able to swim up and to the surface.
In the current version, it seems dwarves will not necessarily drown in 7/7 water so long as there is air directly above them. Dabbling swimmers cannot move while in greater than 4/7 water,Verify but if they can tread water long enough to reach Novice swimmer, they will then be able to swim to safety.
A movie of fortress mode dwarves swimming up and out of a water chamber, without a ramp or stairs. This behaviour needs more investigation: Movie
 Teaching your dwarves to swim
 Waterfall method
The first level is a room with a channel leading to a river. The pressure plate is set to trigger when the water level reaches 7, and is connected to the floor hatches. These then open, draining the water into...
The second level. This room should be set up as a meeting hall or booze stockpile, to ensure it always contains dwarves. Alternatively, you could draft your trainees into the military and station them here. Up to you. I went for the lazy option. The grates in the floor let the water drain before your dwarves drown.
The third level lets the water back into the river, post-waterfall.
 Murky pool outdoor method
Build a large platform with drainage grates above a murky pool. Install pumps and pump water all over it. Then make it a barracks and get your dwarves to spar there. Your dwarves will gain swimming skill and be insulated against cave adaptation as they spar. And you will have to pump one fewer level, in case you don't like using the powered-pump exploit. Also if you use unpowered pumps you could increase your dwarves' toughness even faster. It's also a way to use up some relatively useless real estate (if you simply sparred in the outside, your dwarves would trample the grass.) I haven't actually tried this yet but it should work.
 Swimming pool method
Firstly, build a room to any size specification connected to a pump so that the room fills when the pump is activated. Connected to the same room, make a small tunnel with a ramp upwards at the end and a door somewhere in between. Draft the dwarves which you wish to train and station them inside of this room. Next, lock the door. Lastly, activate the pump, keeping a keen eye on the water level. The ideal water height is 4. However, if you would rather not monitor the water level by eye, you can always hook up a pressure plate to deactivate the pump (or the gear assembly connected to the windmill or waterwheel which powers said pump) at a water level of 4. The dwarves will casually sit there until they learn to swim.
This method works well for teaching miners to swim. Find an unused area of stone/soil directly above an aquifer. Designate that area a channel. Designate every other column a down stairway. The section above the aquifer should now look like this:
>_>_>_>_> >>>>>>>>> >_>_>_>_> >>>>>>>>> >_>_>_>_> >>>>>>>>> >_>_>_>_> >>>>>>>>>
Once this is dug out, designate the aquifer directly below it as up stairways, and let your miners learn to swim. The aquifer layer should look like this:
<~<~<~<~< <<<<<<<<< <~<~<~<~< <<<<<<<<< <~<~<~<~< <<<<<<<<< <~<~<~<~< <<<<<<<<<
The channeling ensures that the miners will get some practice where they MUST swim, but the surrounding stairs ensure they won't drown.