I didn't think it was possible for there to exist a badly-made submarine movie, but I watched this and realized I was wrong. If you know anything about submarines, you'll not like this film very much. Examples? Ok, how about this: The boat (sub's are referred to as "boats" not "ships") is crippled by a torpedo explosion, and the Chief of the Boat announces to the XO (Denzel Washington),"forward ballast tanks damaged. we've lost forward air". The next moment, the boat's main propulsion plant is lost, and the sub is shown heading downward into the depths. Do they move the bow planes / fairwater planes or stern planes to use forward momentum to help the boat rise? NO. Do they blow after ballast (the after ballast tanks are presumably still operational)? NO. What do they do? They just ALL STAND THERE staring at the depth gauge, awaiting their arrival at "crush depth", the depth at which the surrounding pressure of the sea will be more than the pressure hull can withstand and the sub will implode and kill them all. But what saves them? Ah, someone in the Engine Room apparently flicks a switch to start the turbines again! "well, whaddya know, I've started the plant again!" Look, if you suffer an engineering casualty that causes the plant to be lost, chances are you're not going to be able to repair the cause in 5 minutes. Add to this the flimsy character development, the "musical chairs" Caine Mutiny - meets - Keystone Kops command changes, the contrived 'drama' - it's just not believable, folks.
So what to do? I recommend you rent, buy, or borrow "Das Boot" (or its very-well-dubbed version "The Boat"), come home and watch it. Immerse yourself in a real submarine drama. And deep-six this artificial-reef of a movie.