[3] Hydra was anchored at the Nore on Sunday 17 May 1801 (as recorded in the journal of Captain Matthew Flinders of HMS Investigator).

[4] Under the command of Captain George Mundy, for eight years from October 1802 to September 1810, she had an active career in the Napoleonic Wars, including the Blockade of Cadiz (1805-1806).

[9] On 30 January 1804, Hydra and Tribune, operating independently, encountered a French flotilla of 20 vessels off Cape La Hogue, and captured three gun brigs and a lugger.

Captain Bennet of Tribune further reported that he had seen a frigate, which he believed was Hydra, capture a lugger and continue in pursuit of a brig.

However, because the two British vessels were there in different capacities, Hydra being part of a squadron under Admiral Sir James Saumarez, commander of Royal Navy forces in the Channel Islands, and Tribune reporting directly to Admiral George Montagu, Commander-in-Chief, Portsmouth, the division of the captains' shares of the prize money was complex.

[c] After Admiral Lord Nelson defeated the Franco-Spanish fleet at the battle of Trafalgar on 21 October 1805, four French frigates and the brig Furet took refuge at Cadiz, where they remained into February 1806.

To try to lure them out, Vice-Admiral Cuthbert Collingwood pulled his ships-of-the-line ten leagues out to sea, leaving only Hydra, under Captain George Mundy, and the brig-sloop Moselle in close blockade.

On 23 February a strong easterly wind drove the British off their station, which led the French commander, Captain Louis-Charles-Auguste Delamarre de Lamellerie, to seize the opportunity to escape.

Mundy began firing rockets and alarm guns to alert Collingwood, while sailing parallel to the escaping French squadron.

Furet was armed with eighteen long 9-pounder guns, and had a crew of 130 men under the command of lieutenant de vaisseau Demay.

[14] During the next six months, Lamellerie's frigate squadron cruised the Atlantic, visiting Senegal, Cayenne and the West Indies, but failed significantly to disrupt British trade.

[1] From then until finally paying off in 1817 she was employed as a troopship and, in that capacity, for example, Captain Robert Lawson's Company, 8th Battalion Royal Artillery, left Spain on 22 July 1814, on board HMS Hydra, bound for Plymouth.

[16] Under the rules of prize-money, the troopship Hydra shared in the proceeds of the capture of six American vessels in the Battle of Lake Borgne on 14 December 1814.