Thanks. Google Image Search shows examples in marinas. Hence the confusion.
I'd thought about a U-shaped inflatable attachment to a travel trailer. My Clark Cortez had a rear entrance and I wanted to be able to back it up to a docking port on a house. But I never had a house I could modify and the motor home at the same time.
Obligatory VW:
https://www.google.com/search?q=beetle+on+a+houseboat