Project 50 was a late WW1 German design for a submarine which would carry 4 - 150mm guns, and possessed 10 torpedo tubes, which for its time was very impressive. For propulsion, steam turbines were used instead of diesel engines. In terms of size it sits at around 125 meters long and almost 12 meters wide, making it a massive submarine for its time. For comparison U-65 sits at around 70m in length and 6.6 meters wide. Ultimately no iteration of this design was even laid down during WW1 or the interwar years.