Amphibious
The creature can breathe water as well as air and can stay underwater indefinitely without the need to surface.
If this trait is taken by a creature with the ability to breathe another substance other than air (i.e., water, ammonia, carbon-dioxide, etc.) then it can breathe air as well as its native atmosphere.
If this trait is taken by a creature with the ability to breathe another substance other than air (i.e., water, ammonia, carbon-dioxide, etc.) then it can breathe air as well as its native atmosphere.