There is a halachic ruling that you can put a Sukkah on a camel. So if you can put a Sukkah on a camel then why not on a boat? The Chasidim in Venice like to celebrate Jewish festivals on the boats. Here Michal painted Venice Chassidim on a boat in a Sukkah blessing the lulav. You can see on the picture the Canale Ormesini which is right behind the new Ghetto with the iron bridge.