This is a pool built by Agor Engineering that has a wooden floor that can be raised and lowered hydraulically (previously: these concrete ones). You can adjust the height too, so if you just want to sit in tit-deep water and sip cocktails, you can do that. Or you can make it go all the way down and play Marco Pollo. Or you can save yourself tens of thousands of dollars and just buy an inflatable kiddy pool at Target and set that shit up in the front yard and wave at all the cars that pass by. Just don't ask any joggers if they want to join you. Apparently some of them find that creepy.
Keep going for a video showing the whole transformation process.
Thanks to Roland, who prefers his pool unhidden so he doesn't forget he has it.