Hollow Orb Bantrid
Source Galactic Ancestries pg. 88
You or your parent lived for years on a low-calorie but high-protein diet. This caused your foot orb to gain a hollow, lattice-like cell structure that makes it lighter and capable of floating in water. You gain a 20-foot swim Speed. While moving atop the surface of any liquid, you have a swim Speed equal to your Speed (or 20 feet, if higher).