Swamp Born (3.5e Feat)
From D&D Wiki
 Swamp Born [Racial]
Lizardfolk that are borne and raised in the swamps spend most of their time in the water and become expert swimmers.
You gain a natural swim speed equal to your land speed (30 ft.) and you can hold your breath for twice your Constitution score in rounds.
Characters can hold their breath for a number of rounds equal to their Con score.