Create An Underwater Obstacle Courses with Swim-Through Pool Hoops These Swim-Through Hoops are the perfect underwater pool game for kids. Each set comes with four large swim-through hoops that are weighted on one side to keep them upright on the pool bottom. The hoops are three and a half feet in diameter, but can be adjusted to make them smaller for a more challenging course. Buy multiple sets to create longer courses along the entire pool bottom.