I once had the extreme good fortune of riding around in a hot tub with 13 other people on the back of a truck in the middle of a desert. There was no driver -- it was in first gear and moving along at about five miles an hour. When we'd get close to the edge of the desert, someone would jump out, run up to the cab, turn the wheel and we'd have another hour of uninterrupted fun. It was probably the coolest thing I ever did.
Just look at the pictures of the Hot Tug, as it steams gently through Dutch canals (this appears to be available only in The Netherlands for the moment). That's about as relaxing as it gets. And while the Hot Tug may not have the luxury appointments of a big yacht, it has the distinct advantage of not costing millions of dollars. Instead, you and a few of your friends can have the pleasure of hot tubbing around Holland for just under $20,000, a little less if you want the electric version. It also seems that it may be possible to rent one.
When I come across things like this on the Internet, my first reaction is always to wonder if it's a hoax. And it may well be. After all, when you come across something you've never seen before, it's natural to assume someone may be playing a joke. My instinct tells me that this is for real, especially because there's another floating hot tub out there, the Hot Tub Boat. Still, I may have to make the noble sacrifice and go check this out myself in order to be sure.
Hat tip to @FutureBoy.