It is believed that the times of treasure hunters are a thing of the past, but it is not. Recently, a treasure of tens of tons of silver was found at the bottom of the Atlantic Ocean. This is the largest treasure trove of precious metal of all time.
Leonardo da Vinci (1452-1519) made sketches of a submarine and William Bourne, a British mathematician, drew plans for a submarine in 1578. But it was only in 1620 that Cornelius van Drebbel, a Dutch inventor, managed to build a submarine. He wrapped a wooden rowboat tightly in waterproof leather and had air tubes with floats to the surface to provide oxygen. Of course, there were no engines yet, so the oars went through the hull at leather gaskets. He took the first trip with 12 oarsmen in the Thames River — staying submerged for 3 hours.
At 21 minutes to eight in the evening of 3 September 1939, the SS Asthenia, outward bound from Liverpool to Montreal with 1400 passengers, was struck by a torpedo. This was the first attack in the Second World War to be made by the German Navy, and the torpedo was fired by U-30 type VII U-boat, commissioned in 1936. On 10 July 1945, the British steam fishing boat Kned was sunk by mine off Lizard Head, in a minefield laid in August 1944 by U218, a VIID U-boat, commissioned in 1942. Thus the German naval war began and ended in submarine action.