Gosselin joined the Royal Navy in 1778 and as a junior officer had extensive service in the American Revolution, including participating in the Battle of the Saintes in April 1782.

His final services at sea in 1809 included his assistance in the evacuation from Corunna of the army of Lieutenant-General Sir John Moore.

[1] After his release he joined the ship-of-the-line HMS Barfleur, the flag ship of Rear-Admiral Sir Samuel Hood, on 11 October 1780.

[4][1] In June 1782 Gosselin transferred with Captain Hood to the frigate HMS Aimable, serving in her until the American Revolution ended with the Treaty of Paris in 1783.

[4] On 1 December 1787 Gosselin was promoted to lieutenant, and in September 1788 he was appointed as such to the newly captured sloop HMS Atalante in which he sailed to the East Indies in January 1789 as part of the squadron of Commodore William Cornwallis.

[2] While serving in the English Channel under the now Vice-Admiral Cornwallis, Gosselin and Kingfisher assisted in the capturing of a French convoy carrying wine and naval stores on 7 June 1795.

[7][1] Gosselin stayed with Syren on the Leeward Islands Station and on 20 August 1799 took part in the successful occupation of Surinam by the forces of Vice-Admiral Lord Hugh Seymour and Lieutenant-General Thomas Trigge.

In 1800 Gosselin paid attendance on George III for three months while the latter holidayed with his family in Weymouth, before in February 1801 escorting another convoy of merchant ships to the West Indies.

[7] On 2 February 1804 Gosselin's employment was again assisted by his relationship with the now Admiral Cornwallis, taking command of his flag ship, the ship-of-the-line HMS Ville de Paris in the Channel Fleet.

[8] Gosselin served in Ville de Paris until September when he was given command of the frigate HMS Latona and the inshore squadron of the Brest blockade.

The army dispatches on the Battle of Corunna were written by Lieutenant-General John Hope, Moore having been killed, on board Audacious.

[10] Sir John Knox Laughton described Gosselin as 'a professional officer of real ability' and suggested that he was only not employed further after 1809 because of either his illness or the circumstances of his rich marriage.

[13] Gosselin died at his home in Jersey on 27 November 1857 as an admiral of the red and was buried at St Leonard's Church, Bengeo, Hertfordshire.