First Way

Using magma block or soul sand to create a cross shape underwater, you can break the central block of the cross after the bubble columns appear. When entering the central area surround by bubble columns, you can hear the sound of leaving water and breath underwater forever.

Second Way

Placing a single magma block or soul sand at least one block below the bottom of the sea, you can break the block after the bubble columns appear. When entering the area, you can hear the sound of leaving water and breath underwater forever, just like the first way.