A dry dock will usually be an area below sea level, continuous with the sea. Support can be set up capable of holding the ship upright when there is no water. The ship enters the dry dock, usually with the help of tugboats if the ship is large.
Large hydraulic gates close, separating the dry dock, and the ship, from the sea. After the ship is in place, powerful pumps start to remove the water from the dry dock, pumping it back into the harbour. This process can take a long time.
Some fine-tuning of the ship's position is done by scuba diverss while there is still some water left to manoeuvre it about. It is important that the ship is balanced on its support blocks: if it tumbled it there would be substantial damage.
Once the remainder of the water is pumped out, people can walk around in the dry dock, and the ship can be freely inspected or serviced.
When work on the ship is finished, water is allowed to reenter the dry dock and the ship is carefully refloated.
Dry docks are usually built on the shore; however, floating drydocks are ships which have the same abilities.