The Hermine-Bretagne, an oyster dredger, was built in 1972 at the Sibiril shipyard in Carantec, and was purchased by Adramar in 2000. It measures 18 metres long by 6.7 metres at its widest point. Its open deck, shallow draught, low freeboard and powerful cargo booms were all good reasons for repurposing it for use at the underwater archaeological site.
In 2000, the ship was fitted with a hydraulic crane capable of lifting loads of more than two tonnes, a powerful motor-pump supplying power to the underwater suction water dredges, a rear platform and twenty diving outfits. A 20-foot-long metal container installed on the deck was used as an office and technical room.
From 2003 to 2005, the ship was given a second, more thoroughgoing overhaul. The container was replaced by wooden superstructures, including a mess-cabin, an office, a workshop, bathroom facilities and a wet-room. A rear gantry, a fore windlass and a second diving platform were also added during this overhaul. Following the Archéonaute's withdrawal from active service in September 2005, and prior to the arrival of the André Malraux in late 2011, this overhaul made the Hermine-Bretagne the best-adapted and most functional support vessel for underwater archaeology on the entire French coastline.