Hydra-class minelayer
 The Hydra class were two minelayers of the Royal Netherlands Navy built to serve in the Dutch East Indies and Dutch territorial waters in Europe. The construction of the ships began in 1910 and was completed in 1912. The ships were built by the navy yard (Rijkswerf) in Amsterdam. Both ships were still in service during the Second World War. Only the Medusa escaped to the United Kingdom however. The Hydra was lost after it was fired on by an anti-tank weapon. It sank in the waters off Zeeland.