Designed by naval architect Giancarlo Zema, it's a unique four–level house, consisting of, from the top down:

1) The living area

2) An observation deck

3) A boat dock

4) An underwater observation globe

The floors are connected via a winding staircase facing the sea and a glass elevator.

The underwater observation globe comes complete with lighting and "diver lock–out options."

[via AW]