HMS Hydra (Pennant Number A144) was a Royal Navy deep ocean hydrographic survey vessel, the third of the original three of the Hecla class. 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 (see http://www.clydesite.co.uk/clydebuilt/viewship.asp?id=1592) and first commissioned on 4 May 1966 and, as the replacement for the survey ship HMS Owen http://www.navyphotos.co.uk/lchcrrn2b.jpg, her commanding officer and many of her ship's company formed the first commission of HMS Hydra.
Eight ships of the Royal Navy have been named HMS Hydra after the hydra of Greek mythology. The ship's badge is a representation of the hydra as a serpent with seven heads http://images.google.co.uk/imgres?imgurl=http://www.flagsandcrests.net/images/hms/hydra.jpg&imgrefurl=http://www.flagsandcrests.net/hms9.html&h=154&w=120&sz=6&hl=en&start=20&tbnid=X9xbWCVT9sDUFM:&tbnh=96&tbnw=75&prev=/images%3Fq%3Dhms%2Bhydra%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DRNWH,RNWH:2005-14,RNWH:en The ship's motto was Ut Herculis Perseverantia (Latin: "Like Hercules Persevere").
HMS Hydra (J275) was an 850 ton Algerine class minesweeper of the Royal Navy.
HMS Hydra launched in 1838, at Chatham Dockyard, was a wooden steam paddle sloop of the Royal Navy of 818 tons (builder's measurement). She was rated at 220 horsepower and carried 6 guns.
HMS Hydra was an Acheron or "I" class destroyer of the Royal Navy displacing 770 tons.