It's the hunt.
Getting into a good firing position undetected.
Avoiding depth charge attacks.
One of my favourites is sneaking into a shallow harbour and attacking ships in there and then getting out in one piece.
Although I have to say,out of the box it is still playable,once you start adding mods you can make it as realistic as you like and improve it no end.
A big factor is that I find Subs fascinating so I have a real interest in the game.
When I mention to my game playing mates that I play a Sub sim they start making 'ping' noises and take the p**s but I don't care
