You need a 3 x 5 ft floating laminate of artificial turf with Velcro fasteners and twelve floating wiffle practice balls, also layered with Velcro strips. It makes for a three-hole game between two people, with the players taking a dive to dig out the ball each time.
Water Balloon Volley
This requires several water balloons, a net and a swimming pool. One team begins the game by throwing a water balloon over the net to the other team. The opposing team must try to catch it without breaking it. When a balloon breaks, the team throwing it scores a point.
Set up a net at each end of the pool and divide players into two teams. Each team tries to get the ball into the net to score one point. Players may touch the ball with only one hand at a time, and can't hold it underwater. When players don't have the ball, they can't rest their feet on the bottom or sides of the pool.