Water Adaptation( Races of Faerûn, p. 170)
You favor your aquatic elven parent and have developed the ability to breathe and move about in water easily.
You can breathe water as well as air. You gain a swim speed of 20 feet, which means you can move through water at that speed without making Swim checks. You gain a +8 racial bonus on any Swim check. You can always take 10 on Swim checks even if rushed or threatened when swimming. You may use the run action while swimming, provided you swim in a straight line