When you want a house on the water.
My dad and his buddies once built a floating cabin out of hurricane wreckage that hung out in the marshland (southern sound area--interior outer banks to you carpet bagging yanks) along the southern NC coast, within their clam leases. It wasn't nearly as badass as that one, but it had space for 4 to sleep, a sink with a drain that doubled as a shitter (by taking the 5 gallon catch bucket to the isolated ocean-side shore with you) and a detachable dock for another 2 to sleep (and lazily drift away from the cabin during the night because the snoring within would always be unbearable). It was the most hurricane-proof structure in the area, because it would just ride the water and wind and beach itself somewhere that it felt appropriate, and so just needed to be found later and towed back into place.
bastard town forced them to burn it down after about 10 years because all the local teenagers (brave water skunks that could actually navigate a boat out through the marsh) would use it to get drunk, high, fuck and all sorts of inappropriate behavior.....which meant no one else could do the same anymore.