After the disaster of the poorly constructed and performing Biber German midget sub, the next endeavor was the excellent Seehund (Sea Hound) which was 15 tons, 39 ft long, and was powered by a 60 hp Bussing motor to a speed of 9 mph. Was armed with 2x 533mm torpedos. It was difficult to spot and did not appear on radar. When attacked by depth charges it rolled with the waves and survived most of the time. Construction was by prefabrication and then trucked to the assembly area and sheltered in hardened bunkers immune to bombing. Almost 300 of them were built for 1945 with another 200 under construction. They operated in the Straight of Dover and N Sea in small groups of no more than 30 at one time. Losses in just 15 weeks of operation was 10% and yet they caused the British to deploy 500 escorts and 1000 aircraft to fight these small groups and attack their fortified bunkers! The Seehunden sunk 40,000 tons in a short time, although the British only reported 19,000 tons with an additional 19,000 tons damaged. The German historian claims 120,000 tons which is just too high. Most good sources claim anywhere from 20-60,000 tons. So 40,000 is in the middle. The Free French frigate Le Combattante was lost on Feb 23, 1945 after being hit by a single torp from a Seehund. Most Seehunden were dropped by S-boots. After the war the British studied the Seehund intensely. They were captured at Kiel, Elbing, and Ulm.