If you want a sub-sim and still possess a clunker (i.e., 286 or earlier), then this is the game for you.
It gave me something to do besides homework. Of course, I did enjoy sinking ships, which was fun to do when you are 14.
The lack of AI. I quickly figured out an easy strategy for sinking ships. I'd run around, making as much noise as possible to attract the destroyers. Once I knew they were in-bound, I'd release a ton of mines as I submerged, then I waited. Given a few minutes and I had sank the entire escort force. Finding and sinking merchant ships after that was easy. Also, rescuing pilots was a very boring effort. It was a lot like trolling for fish, wandering around until the computer decided you found him.
The Bottom Line
It's a very simplistic submarine game played in a WWII environment. It is essentially you against the Japanese Navy and Merchant Fleet. The only ally you have is the sub tender who'll come out and give you more fuel and ammunition. There is no resemblance between the map you work with and the real world, just a bunch of islands for you to navigate around.