A submarine is not just some tin can. It's a cold, dark room full of dials and buttons, where it's decided whether you come home or stay on the bottom. Silent Hunter understood this and made it better than ninety percent of games from the same era.

You go in as a commander of a German U-boat in the Second World War, with a map, with convoys, and with limited fuel. It's not action, it's waiting and math. You calculate the route, listen to the hydrophones, wait for the right moment and press fire. Then headphones again, silence again. The game forces you to think like a commander, not like a player spraying bullets at everything that moves.
The graphics are minimalist — surprisingly, because you won't see and won't hear the graphics and sound. You see a window with the ocean, a map, windows with data. Sound? The sound of hydrophones, tapping your hand on the hull, distant explosions. That's all you need. The game happens in your head. You imagine where the enemy is, how far away, where his escort ships are. Just the two of you alone in the dark.
The controls are simple, commands flow naturally. You set a course, a depth, let the submarine move. Time runs at accelerated tempo. Modern simulators made it easier, but this is older, tougher. When the submarine breaks, there's no one to blame. You brought it on yourself with a bad decision.
Silent Hunter became a classic precisely because it got it right. It wasn't an average simulator weighed down by animations. It was a pure idea — commander, water, enemy. Four years later came the successor and that one already had models and 3D, but here, at the origin, there's something more juicily direct. The submarine physics aren't perfect, but they give you what you need to know.
Today it's mainly a thing for those who want to test whether quiet fear is more interesting than loud carnage. Crowds of unnecessary UI and tutorials won't bother you — you'll pay for it by looking at this game as game reading, not as entertainment in the classical sense. But once it opens in your head, you won't want it any other way.