Amphibious (3.5e Feat)
From D&D Wiki
You were born capable of breathing and living both on land and in water
Prerequisite: 1st level only.
Benefit: Due to racial lineage, arcane pollution, or some mutation, you are capable of breathing in water as well as you do on land (and vice-versa for aquatic races).
Normal: Character would only be able to exist in one environment
Special: You may only take this feat at 1st level.