Before dry docks, crews careened ships by grounding them at high tide and waiting for the water to drop, as the English warship Grace Dieu was bedded in the mud of the River Hamble in 1434 behind a brushwood and clay wall. This episode follows the long effort to empty water from around a hull instead. The Phoenicians built covered slipways at Kition in Cyprus around the 5th century BC, and Carthage had up to 180 dry dock ramps that Rome took over in 146 BC. Athenaeus described a flooded and drained trench for Ptolemy IV’s giant tessarakonteres around 221 BC, a claim historian Joseph Needham disputed for lack of physical evidence. In 1088, Shen Kuo’s Dream Pool Essays recorded a basin at Jinming Lake where water wheels drained water so two 200 foot imperial dragon ships settled onto beams, after which the basin was roofed as a hangar.

Europe’s oldest surviving dry dock, built at Portsmouth in 1495 for Henry VII, was sealed with a rock and clay bank that took up to 29 days to dig out and was drained by horse powered bucket chains. Modern graving docks use gates, steam pumps, and a docking plan of keel and bilge blocks placed under a ship’s load bearing ribs while divers guide the landing. Floating docks sink by flooding their ballast tanks and rise by pumping them out, and the same idea now builds storm barriers and tunnels.

• Engineers cut recesses into dock floors so the bulbous sonar domes of anti submarine warships hang free.
• Britain towed an iron floating dock across the Atlantic to Bermuda in 1866 because the porous limestone ruled out a graving dock.
• The U.S. Navy’s World War II AFDB-1 floating dock was 1,000 feet long and assembled from sections at bases like Guam.
• In 2018 Russia’s PD-50 sank after a power failure, dropping a crane onto the carrier Admiral Kuznetsov.
• The Oosterscheldekering’s 65 concrete piers, each 18,000 tons, were built in a dry dock and floated out.