Sunken Song

Perform (sing) 4 ranks, Bardic music class feature,

By tremendous effort of will and sheer musical ability, you can use Perform (sing) underwater even though you cannot breathe water. This is more like a forceful humming than singing, and words are not intelligible, but you are able to produce bardic music effects. The maximum distance of such effects (where applicable) is unchanged. This feat does not help with Perform checks involving oratory or wind instruments.

You cannot use any air-dependent Perform skills underwater if you are not able to breathe water

By tremendous effort of will and sheer musical ability, you can use Perform (sing) underwater even though you cannot breathe water. This is more like a forceful humming than singing, and words are not intelligible, but you are able to produce bardic music effects. The maximum distance of such effects (where applicable) is unchanged. This feat does not help with Perform checks involving oratory or wind instruments.

You cannot use any air-dependent Perform skills underwater if you are not able to breathe water

You can project your voice underwater.