I live near Holland, where water is everywhere, and where, at some time, the houses prices were crazy.
Some people did let build a house on water.
Main advantage is, when you have to move to another location for your work, you take under tow your waterhouse with you to another city.
Bigger than a RV anyway, if you wish.
https://www.holland.com/global/touri...dam-canals.htm
It also exists in the States, in Florida's keys or t Seattle, i.e.
https://www.realtor.com/news/unique-...at-in-seattle/