Welcome to Subsim andamarine.
You are in good company liking submarine movies like Das Boot and Submarine and Naval simulators like Silent Hunter. Most if not all of us here in the forum do as well.
Most here have said Silent Hunter 5 is good with modifications added. Give it a try and see how you like it as compared to SH3 and SH4. These are both great as well with modifications added.
Luckily you can have and try them all and not have to make a choice.
Enjoy.