HMS Hydra (pennant number A144) was a Royal Navy deep ocean hydrographic survey vessel, the third of the original three of the . The ship was laid down as yard number 2258 on 14 May 1964 at Yarrow Shipbuilders, at Scotstoun on the River Clyde and launched on 14 July 1965 by Mary Lythall, wife of the then Chief Scientist (Royal Navy), Basil W Lythall CB (1919–2001). She was completed and first commissioned on 4 May 1966 and, as the replacement for the survey ship , her commanding officer and many of her ship's company formed the first commission of HMS Hydra. She was decommissioned and sold to the Indonesian Navy in 1986 and renamed KRI Dewa Kembar (Pennant Number 932); she was still in service in 2019. Ship's name and battle honours There have been eight ships of the name in the Royal Navy, named for the Hydra of Greek Mythology, a serpent with many heads (though nine is generally accepted as standard), the centre one of which was immortal. The monster was overcome and slain by Hercules. The ship's badge of HMS Hydra depicts the monster with seven heads. The ship's motto was Ut Herculis Perseverantia ("Like Hercules Persevere"). Late 1960s In the month after first commissioning Hydra carried out machinery and equipment trials and embarked stores at Chatham, before sailing for surveys in the North Atlantic. Based in Reykjavík, an extensive area south of Iceland was surveyed between June and September 1966. She then visited Copenhagen and for the remainder of 1966, was employed in searching for wrecks in the shipping lanes of the North Sea and the approaches to the Dover Strait, before returning to Chatham in early December for her winter lie-up. March 1967 saw the ship carrying out a short survey of the critical depths at the entrance of the Black Deep Channel in the Thames estuary. She then carried out a major survey of the bathymetry, gravity anomalies and total magnetic field in a large area of the Atlantic Ocean, covering the North-West Approaches to Britain. At the same time, between May and August 1967, a detached party and the ship's two surveying motor boats undertook a survey of the fishing port of Burtonport, Donegal. After summer leave and maintenance and a visit to Brest, she spent a fortnight on oceanographic surveys in the Azores area, followed by a visit to Lisbon and