Rolex invented the water-resistant Oyster case in 1926, raising the possibility of a watch that could be used in the water. The Oyster Perpetual upped the ante by eliminating the need to unscrew the crown during use. The Rolex Oyster watches (with hand winding movements by Cortébert) formed the basis for the first dive watches, jointly developed by Rolex and Panerai in the 1930s.