My two dogs. We have more fun playing with the dogs in the pool than any two grownups should reasonably have. We play catch, we play chase, we dunk them, they dunk us, we swim laps together, we throw stuff - they fetch it, and all the while they aerate the water and stir up the dirt on the bottom and keep it flowing through the skimmer. All that activity and splashing keeps deerflies away, a total added bonus to swimming with dogs.