Sea explorers announced Monday the discovery of a new sunken treasure that they plan to retrieve from the bottom of the North Atlantic.

Off Ireland in 1917, a German torpedo sank the British steamship Mantola, sending the vessel and its cargo of an estimated 20 tons of silver to the seabed more than a mile down. At today’s prices, the metal would be worth about $18 million.

Odyssey Marine Exploration, based in Tampa, Fla., said it had visually confirmed the identity of the Mantola with a tethered robot last month during an expedition and had been contracted by the British Department for Transport (a successor to the Ministry of War Transport) to retrieve the lost riches.

In recent years, strapped governments have started looking to lost cargoes as a way to raise money. They do so because the latest generation of robots, lights, cameras and claws can withstand the deep sea’s crushing pressures and have opened up a new world of shipwreck recovery.