This, in the North Sea and others with high wave heights up to 30ft. Many major sea battles contain some episode of miss identification of well known surface vessels even by airborne observers. Once one ship has been sunk under controversial circumstances, in a war you dont hear the other side, who would blame a captain for ramming a submarine and /or running?WW I periscopes weren't all that good to begin with let alone using an observation position lower than a man sitting in rowboat. .