Course To Senegal
On 17 June 1816, a convoy under the command of Chaumareys on Méduse departed Rochefort, accompanied by the storeship Loire, the brig Argus and the corvette Écho, to receive the British handover of the port of Saint-Louis in Senegal. The Méduse, armed en flûte, carried passengers, including the appointed French governor of Senegal, Colonel Julien-Désiré Schmaltz, and his wife Reine Schmaltz. The Méduse's complement totaled 400, including 160 crew. She reached Madeira on 27 June.
Schmaltz then wanted to reach St. Louis as fast as possible, by the most direct route, but this would take the fleet dangerously close to the shore, where there were many sandbars and reefs. Experienced crews sailed further out. The Méduse was the fastest of the convoy and, disregarding his orders, the captain quickly lost contact with the Loire and the Argus. The Echo kept pace and attempted to guide Méduse, but to no avail. The Echo then prudently moved further out to sea.
Chaumareys had decided to involve one of the passengers, Richefort, in the navigation of the frigate. Richefort was a philosopher and a member of the Philanthropic Society of Cape Verde, but had no qualification to guide ships. As she closed on the coast of Africa, the course of Méduse became dangerous. Richefort apparently mistook a large cloud bank on the horizon for Cape Blanco on the African coast, and so underestimated the proximity of the Bank of Arguin off the coast of Mauritania.
On 2 July 1816 Méduse ran into increasingly shallow water, both Chaumareys and Richefort ignoring signs such as white breakers and mud in the water. Eventually, Lieutenant Maudet took it upon himself to start taking soundings off the bow, and, measuring only 18 fathoms, warned his captain. Realising the danger at last, Chaumareys ordered the ship brought up into the wind, but it was too late, and Méduse ran aground 50 kilometres off the coast. The accident occurred at a spring high tide, which made it difficult to re-float the frigate. The Captain refused to jettison the 14 three-tonne cannons and so the ship settled into the bank.