a vessel transfer system utilizes a larger , surface effect vessel with a hull and a cargo deck , having a pressurized volume of air under its hull . the larger vessel cargo deck is lowered relative to a water surface in order to receive a smaller vessel . lowering is achieved by depressurizing the volume of pressurized air under the hull . movable propulsors on an air cushion vehicle permit efficient operation under way in an outer position , while minimizing the envelope dimensions for stowage in a well deck , providing clearance from bridges , docks , etc . in an inner position . in the outer position , the propellers operate in more uniform inflow conditions , resulting in improved performance and lower noise levels . in addition , the craft can be arranged to use a full width stern ramp resulting in time saved during cargo loading / unloading . the propellers will be less likely to ingest green water in high sea states .