You know how to swim and can do so even in stormy water.
Check: Make a Swim check once per round while you are in the water. Success means you may swim at up to half your speed (as a full-round action) or at a quarter of your speed (as a move action). If you fail by 4 or less, you make no progress. If you fail by 5 or more, you go underwater.
If you are underwater, either because you failed a Swim check or because you are swimming underwater intentionally, you must hold your breath. You can hold your breath for a number of rounds equal to twice your [pfr_gettingStarted#constitution|Constitution] score, but only if you do nothing other than take move actions or free actions. If you take a standard action or a full-round action (such as making an attack), the remainder of the duration for which you can hold your breath is reduced by 1 round. (Effectively, a character in combat can hold his breath only half as long as normal.) After that period of time, you must make a DC 10 [pfr_gettingStarted#constitution|Constitution] check every round to continue holding your breath. Each round, the DC for that check increases by 1. If you fail the [pfr_gettingStarted#constitution|Constitution] check, you begin to drown. The DC for the Swim check depends on the water, as given on the table below.
| Water | Swim DC |
|---|---|
| Calm water | 10 |
| Rough water | 15 |
| Stormy water | 20* |
| * You can't take 10 on a Swim check in stormy water, even if you aren't otherwise being threatened or distracted. | |
Each hour that you swim, you must make a DC 20 Swim check or take 1d6 points of nonlethal damage from fatigue.
Action: A successful Swim check allows you to swim a quarter of your speed as a move action or half your speed as a full-round action.
Special: A creature with a swim speed can move through water at its indicated speed without making Swim checks. It gains a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. The creature can always choose to take 10 on a Swim check, even if distracted or endangered when swimming. Such a creature can use the run action while swimming, provided that it swims in a straight line.
If you have the [pfr_feats#athletic|Athletic] feat, you get a bonus on Swim checks (see [pfr_feats|Feats]).