Submarine Fitness Grip Ball
A Sports Training Ball for Aqua Athletes.
By setting the amount of water to air ratio inside the ball, you can set the ball to hover at a depth halfway between the surface and the bottom of a pool or just set it at at whatever depth you desire. The ball would have strong grip handles so divers can retrieve it. This would be great to train for many water-related careers, for lung capacity building, or for general overall fitness.