Depending on where in Venice that your ship is docking, you will need to either walk or take a water taxi to P. Roma. From there, you can take a land bus or land taxi to the Courtyard at the airport. If you want to store your luggage for the day before heading to the hotel (which I recommend so as to avoid backtracking), I think there may be luggage storage at the Santa Lucia train station in P. Roma. Here are some suggestions but I'd verify them beforehand. http://europeforvisitors.com/venice/articles/venice-left-luggage.htm Have a great trip!
We did following and worked like charm: 1. After arriving at the Venice Cruise Port, from the Port a bus took us to the P. Roma ~ 2 minutes ride. 2. From P. Roma we took the local “Bus # 5” directly to the Marriott Courtyard (~15 minutes max); we checked in early in AM. 3. Then took the bus back to Venice (P. Roma). The bus stops at the Marriott CY, it gave us peace of mind knowing that our bags were at the hotel, also there was no need to find baggage storage, carrying the suitcases over many steps, walkways is not the easiest thing to do at all. Also, do not be concerns that you may waste ~ 45 minutes going and coming with the bus to and from the hotel. (the so called backtracking). Also the Venice International Airport is ~ 5 minutes away from the MR CY.