He served under Robert Surcouf and Jean-Marie Dutertre, and was held as prisoner-of-war aboard Royal Navy prison hulks for eight years before being captured before being repatriated at the conclusion of the Napoleonic Wars, continuing his career as a painter until his death in 1857.

For lack of official ships, Garneray joined the Confiance ("the Trust") of Robert Surcouf as an ensign, from April at December 1800.

He sailed on various trading ships during the peace of Amiens, after which he served aboard the Pinson ("the Finch"), a cutter based in Île Bourbon.

Wounded, Garneray was transported to England and spent the eight following years in prison hulks off Portsmouth (on the Protée, the Couronne ("Crown") Vengeance and Assistance.

Probably thanks to one of his brothers, himself painter and engraver and who knew people in the entourage of Napoleon, he received his first official order: the meeting of l'Inconstant and the Zéphir, as an anecdote of the return from Elba.

The work was carried out only in 1834 as, because of the political climate of the Bourbon Restoration, he felt it more convenient to paint the Descent of the French emigrants at Quiberon, which was exhibited at the Salon de Paris in 1815.

He experienced a short return of glory towards the beginning of the Second French Empire, as he was awarded the Legion of honour in 1852 by vice admiral Bergeret and the Emperor himself.

Developing a tremor which prevented him from writing and which complicated his work as a painter, he died in Paris in 1857, a few months only before his wife was mysteriously assassinated.

Garneray was buried at the Montmartre cemetery: A close friend of his had the tombstone decorated with a painter's palette, a ship mast and the Legion of Honour.

Garneray's memoirs were published in three volumes as Voyages, Aventures et Combats,Mes Pontons, and Scenes Maritimes.

They were probably partly rewritten by professional writers, notably Édouard Corbière, introducing spectacular but irrealistic elements: Richard Rose's detailed analysis of the materials used in the writing of Mes Pontons (The Floating Prison 2003, 2012) shows the general unreliability of Garneray as a writer of verifiable history.

However, Sentant fort le goudron and Mes Pontons do constitute testimonies of everyday life in the navy of the time.