The Indian Navy's guided missile frigate, the INS Betwa, tipped over during an undocking protocol at Mumbai dockyard on Monday.
The accident occurred when the docking mechanism failed, Navy spokesman Captain DK Sharma confirmed, adding that the warship tipped over.
The ship was at the 'Cruiser Graving dock' in Mumbai. The dock is under the Indian Navy's jurisdiction and the warship was to go out to sea after a re-fit.
The INS Betwa is a 3,800 tonne guided missile frigate. It was commissioned in 2004.