Forget overpriced gym memberships and jogging in sweaty overcrowded streets. Forget the swanky and uptight Chelsea Piers. For $2 you can splash and giggle and dolphin-dive in Riverbank State Park's enormous indoor and outdoor pool complex. Rec swim is a community event, a rare treat in this anonymous urban-indoor-gym world. You'll dodge elaborate pool games and swimming lessons as you shriek and somersault amid watery mayhem. Lap swimming is available for the more sedate or serious athletes. The rest of us prefer wriggling around, pretending we're five as we try to avoid getting dunked.