If your bored, go to your basic.cfg, take a boat you rarely use. For me that would be the VIIB. In a specific year, go to the value that holds what supercharger that boat comes equiped with. Default is probably -1. Super charger ID numbers are 1260 and 1261. Type in 1262 instead. (thats the snorkel).
Start a single mission, and watch the fun
No need to start the engine, you have a ramjet in your uboat.
You'll havea uboat doing something like 1260 KM. It will gain so much speed, it will nose up out of the water like a hydrofoil. Any bump, depending on how you hit it, will either send you high into the air, or send you crashing into the depths spinning like a top. you just keep going and going until your crash into something. I swear, if get lucky and hit a wave right, you could probably send a boat flying over the english isles.