DO NOT use antifouling to protect underwater metal. That paint is designed to go over the normal hull paint and keeps barnacles and weed from growing. It is POROUS and is designed to gradually wear off to keep fresh poisons near the surface. It will put TOXIC chemicals in your pool!
Sorry for all the caps, but I own a yacht and know a bit about this, and you don't need antifoul, just a good quality epoxy paint over a well prepared surface.