What are facts about U-Boats?

the Germans' launhced the 1st U boat in 1906 and from the German word- U boat-meaning (underseaboot) the meaning explains what type of ship the U boat was like. like a submarine, but even bigger, it's modified karp was 139 feet long, displaced 239 tons, and had a range of 2,000 miles, a surface speed of 11 knots, and a submerged speed of 9 knots, and was joined by it's twin- U-2, in 1908.