Jan Adriaenszoon Leeghwater

Jan Adriaenszoon Leeghwater (1575–1650), born at De Rijp in North Holland, was a Dutch millwright and hydraulic engineer. In 1605 he patented a diving bell for underwater work. He helped drain the Beemster, completed in 1612, and later the Purmer, Wormer and Schermer lakes.

In 1629 he drained the marshes around besieged 's-Hertogenbosch for the Dutch army, and his 1641 book urged draining the Haarlemmermeer. He also improved the rotating-cap windmill and died in Amsterdam.