Living Submersible

You expand your body and fill it with breathable oxygenated fluid. When you do this, your body increases its size to Huge, and your Speed becomes 0. In this form, you can carry up to six Medium or smaller willing creatures. You remain in this form as long as you're in water, or until you choose to revert to your normal form as a single action; otherwise, this ability lasts one hour per level.