You have to collect your luggage off the conveyor belt and take it through to the coach. Depending on how much there is it is either loaded onto the coach or onto a separate lorry and taken to the ship. Either way you don't have to touch your cases at the port as they will be put on the ship and taken directly to your cabin. This may take a few hours due to the sheer volume. Flights are usually dedicated to the cruise unless it's from smaller airport where it may be difficult to fill with cruise only passengers.