Water Supremacy

You gain a +2 enhancement bonus on Swim skill checks. This bonus increases by +1 for every five wizard levels you possess. In addition, you can hold your breath for a number of rounds equal to four times your Constitution score before you must start making checks to avoid drowning.
At 10th level, you gain a swim speed equal to your base speed.
At 20th level, whenever you make a Swim skill check, assume the roll resulted in a natural 20.