last week there was an interesting report in our TV about the submarine U31 on its transit from its base in Eckernfoerde at the Baltic sea to Plymouth to join some manoeuvres together with the Royal Navy. On the transit through the North Sea they got into a heavy gale. Unfortunately the report is in German only but the pictures speak for themselves. The submarine was commanded to do the transit surfaced but in that gale submerging in the shallow Waters of the North Sea wouldn't have provided much benefit to the Crew.
That submarine is a member of the modern class 212A with AIP (Air independent propulsion) by a fuel cell system and just a giant brushless propulsion motor.