It's an architectural trick that can fool your brain into thinking the house is larger than it really is. It's more common on terrestrial dwellings though, rather than the aquatic ones.
On the outside chance that people don’t know this already, it’s a houseboat. It’s being moved from the inner bay to elsewhere. Love the jokes though. :)
Okay, but look. When I was 8 and first head the term “houseboat” this is exactly what I pictured, except my version had a garage where you could launch smaller boats from.