In Venice you have two options; hire a van (probably cheaper) or get a water taxi. Going to the cruise ship - get a van or land taxi or use the cruise line shuttle system.
Going to a hotel is different. You need a water taxi or you must be ready to carry your own bags for quite a distance.
The water taxis line up outside the airport. The advantage with them is that they can take you directly to your hotel no matter where it is located within the city of Venice. A Van can only take you to the train terminal which is sort of the "land gateway" to the city of Venice where the streets are all canals.
Everyone in Venice travels by boat or walks. If your mobility is limited, you will need a boat. Expect to spend over E100 (Euros) on a water taxi each way from the hotel