Copenhagen - Said to be the largest private-built submarine in the world, “Nautilus”, sank at night Aug 10 at Kastrup Havn, Copenhagen, Denmark. Owner and builder of u-boat, Danish entrepreneur and inventor Peter Madsen, jumped into water and survived ordeal. There were no other persons on board. Submarine said to be already located by Navy. UC3 “Nautilus” was built in 2008, tonnage 40 GT, length 18 meters, crew 4-8, propulsion diesel engine and electric motor.