Pool with waterfall & grotto with jacuzzi. Drake's Disneylike Grotto Estate - Celebrity Homes and Pools. I've ALWAYS wanted a pool like the grotto in pirates of the Caribbean when you first splash down!
Devil Spring - one of seven springs that are located in the private Ginnie Springs park (northern Florida), a cave divers paradise. For non-divers there is still plenty to see when snorkelling. The intense blue colour is due to the water depth at the cave
Indoor swimming pool in tunnel underneath house - This would be obscenely expensive, but I think the idea is pretty cool. Having a pool that resides in a tunnel underneath your house is wholly unnecessary, but a pretty dope idea in terms of indoor pools.