There is plenty of room to land a plane or helicopter on our large aircraft carrier. Check out the flight deck, galley, bridge, or go upstairs for a view from the control tower deck. Downstairs is a large access way for submarines. There is also an alternate top side entrance by the equipment service elevator at the other end of the ship.

A free submarine for members is at the lower level. Don't hold your breath because submarines have have air and underwater vision. From here dive down and head South East to the secret underwater base. Look for the sea lanterns that light the submarine landing port. Members get a free raft for completing the Vehicle Tour!

This completes my goal of riding a bike to the Carport, a car to the Airport, a plane to the Seaport, and then a submarine to the Underwater Base!

Thank you Zoomy6900 for your help, and thank you Bacon_Mister for the aircraft carrier, and the under water base structure from the Publichog server.