de Graaf was a Dutch 20-gun sixth rate frigate, constructed some time before 1781 to the following dimensions: 104feet along the gun deck, 90feet at the keel, with a beam of 27feet and a depth in the hold of 10feet. She measured 363 tons burthen by calculation, but was locally, and incorrectly, reported to be of 514 tons burthen. Her armament was made up entirely of 9-pounder long guns and she had a crew of 160 men.
In February 1781, during the Fourth Anglo-Dutch War, de Graaf was serving at the island of Sint Eustatius. On 4 February she was captured, along with the island as a whole, by an invasion force commanded by Admiral George Rodney. She was taken into service by the Royal Navy and renamed Saint Eustatius, after the island at which she was captured. She was commissioned on 14 February by Captain George Bowen on the Leeward Islands Station, but later on in the same year Bowen was replaced in command by Captain Andrew Sutherland. In January 1782 Captain Lord Cranstoun took command of Saint Eustatius, and then on 30 April he was replaced in turn by the newly promoted Captain William Carnegie, who then left the ship on 13 January 1783.[1] The cycle of captains for the ship continued, with Captain Richard Grindall assuming command in March, and Captain William Smith replacing him only one month later. Having had six captains in only two years of service, Smith was Saint Eustatiuss last; she was sold at Antigua later in 1783.