Not awful but...
... it definitely won't wind up in anyone's Top Ten List of Great War Films. More likely the Top Ten List of Mediocre-at-Best War Films.
I can't and won't comment on historical accuracy. That aside what really knocks this film down is the awful CGI which was distracting.
The clearly limited budget required some creative film making. For example, some of the upper decks scenes appear to have been filmed on a real warship. During the sinking, they clearly couldn't angle the warship so they do the old 'Star Trek' trick. The cameras are angled and the actors then run oddly to suggest the ship is sinking. Nic Cage's spastic sideways run to make it seem he's running uphill is a thing to behold...
That said, I was impressed with the scenes of men floating in the open ocean while the sharks swim lazily between them before picking them off. How was THAT done?
The acting is fine, not outstanding. The story is somewhat lopsided too... we see a lot of the American side of the event, but just enough of the Japanese side to make them more sympathetic. However, it's not enough to underscore the emotional final scene at the end of the movie where the two captains come face to face shortly after the war.
Not the worst way to kill a couple of hours, but you'll forget it pretty quickly.
Robert Shaw as Quint in Jaws told the same story in four minutes with more power and emotional punch so you can save yourself some time by just watching that instead. It's on YouTube.