The Hotel Principe is located right on the Grand Canal not far from Piazzale Roma and the train station. The only way to get direct water transfer is to take a private water taxi from the airport to the hotel. All other options involve some degree of walking/bus/taxi etc. Even from the airport, it will be a short walk to the dock, but this should be manageable.
I have included a few links to private water taxi services. We have never used this type of service so I can’t recommend a specific company. A Google search should also provide a list of companies that provide this service.