The truth is, I've had my feelers out for a very old submarine simulator game for a long time called 688 Attack Sub (with a patch for your jacket!), but I've yet to find a complete package at a price I'm willing to spend today.
In the meantime, I've had Silent Service on my radar and found a beautifully pristine copy for only $10. I'm looking forward to doing a deep dive with it soon (Oh! With the puns!). Silent Service was an early game made by the legendary Sid Meier of Civilization fame.
Silent Service was one of Meier's earlier simulation works, prior to Pirates! and Civilization. In any case, it looks and sounds pretty fantastic and - most importantly - the original disk is still fully functional.