A great submarine game with only a few little drawbacks:
Upsides:
It feels surprisingly varied, with huge emphasis on the details. This makes it very fun to play even after many hours. There are many random events (radio transmissions hinting you to other targets, changing orders by the Commander of the submarine arm, calls for help by other submarines, etc.), different missions (tonnage war/blockade service, mining, hunt for certain individual ships, spy missions, etc.) and different theatres of war with different types of submarines.
Downsides:
While the submarines get new weapons and other features unlocked progressively during the game, the opponents don't. So in 1939, you can frequently get a direct hit from British depth charges (Mk. VII, which had two trigger settings at about 40 and 80 m of depth) at a depth of 150 m. They didn't reach this far down and this error and the unrealistic gunnery skill of the depth charge crews of the hostile ships makes things a bit impractical with the original submarines which would still need to get most of the upgrades to be on par with such rather late-war skilled and armed ships.
Ships are counted as damaged or sunk depending on how low they sit in the water. That's generally good, but the levels at which they count as damaged, let alone sunk, is still a bit wild: half the deck is awash, but the ship is still not "damaged" and a ship which has just the bow or stern sticking out while going down still isn't sunk. Similarly, only the outside of the hull takes damage, while firing at the deck or superstructure doesn't cause damage, even though this would sometimes be quite neat to accellerate the sinking of an already struck ship.
The auto-route feature doesn't work well in confined spaces and shallow waters, so you will take damage and beach yourself, if you try to navigate the Kiel Canal on the auto-route plotted course through the canal.
One feature I still would love to have would be the option to just fire a torpedo straight ahead/astern. There just is little use in performing all the course prediction measurements and calculations just to shoot a stationary target 300 m dead ahead.
