You may choose to reroll any Swim check, but the result of the reroll must be accepted, even if it is worse. In addition, you may choose to take 10 on Swim checks, even when distracted or threatened.
An Aqualish may choose to reroll any Swim check, but the result of the reroll must be accepted, even if it is worse. In addition, an Aqualish may choose to take 10 on Swim checks, even when distracted or threatened.
A Gungan may choose to reroll any Swim check, but the result of the reroll must be accepted even if it is worse. In addition, a Gungan may choose to take 10 on Swim checks even when distracted or threatened.