Wikipedia
A shiplift is a modern alternative for a slipway, a floating dry dock or a graving dry dock. A shiplift is used to dry dock and launch ships. It consists of a structural platform that is lifted and lowered exactly vertically, synchronously by a number of hoists. First, the platform is lowered underwater, then the ship is floated above the support, and finally the platform with shipsupport and ship is lifted and the ship is brought to the level of the quay.
Nowadays, shiplift are most of the time supplied under rules of a classification authority. Lloyd's Register of Shipping is the authority with most experience in the certification or classification of shiplifts. Whereas "shiplift" is the word that is normally used, the term used by Lloyd's register is "Mechanical Lift Dock".
The Syncrolift System was invented by Raymond Pearlson, who was later awarded the Sperry Award for the invention, development and worldwide implementation of a new system for lifting ships out of the water for repair and for launching new ship construction.
It is important to synchronize the winches. Modern systems use electrical control and drive systems for the winches. Old fashioned electrically driven shiplift systems needed so much starting current that they often could only be used in the weekend when other electrical equipment was not in use. The modern shiplifts however do not have this disadvantage; they can start the movement in any desired curve.