A dry dock is a facility which serves as a maintenance hangar for water craft. It permits extensive manufacturing, refitting, repair, and even complete overhaul of the components of a ship in the confines of a waterless environment, without the need to completely haul the vessel out of the water.
When a ship is berthed in a dry dock, the outer gates are closed and the water is drained from it, permitting all areas of the superstructure and hull to be accessed by terrestrial sentients. Because the entire hull is removed from the water, it is possible to access all areas of the ship which normally sit below the water line without worrying about leaking, and without having to completely empty compartments to access the remote corners of the ship. Once the work has been completed, the berth can be gradually flooded via a series of baffles and gates to pinpoint areas of the hull where the structural integrity is sub par, causing leaks. Once the berth has been completely filled with water, and the ship's seaworthiness is validated, the outer gates can be reopened, and the ship launched from there.
Even amphibious species, such as the Gungans, prefer this approach to ship maintenance, as it is much easier to fix a hull leak in a meter of water than fifty meters below the surface.