He was the nephew of Jacques Félix Emmanuel Hamelin, a successful rear admiral in the French Navy of the Napoleonic era.

Hamelain went to sea in 1806 as cabin boy with his uncle, Jacques Félix Emmanuel Hamelin, on the frigate Vénus in the era of Napoleon and the French Empire.

The Vénus was part of the French squadron in the Indian Ocean during the Mauritius Campaign of 1809-1811, and young Hamelin had an opportunity of seeing much active service.

During the Crimean War he commanded in the Black Sea, and co-operated with Admiral Dundas in the bombardment of Sevastopol on 17 October 1854.

[1] His administration lasted till 1860, and was remarkable for the expeditions to Italy and China organized under his directions; but it was even more notable for the energy shown in adopting and developing the use of armour.