Character mistake: At the end of the movie, Ramsey and Hunter begin a conversation about Lippizaner horses. Ramsey says they are from Portugal, Hunter says they are from Spain. However, the Lippizaner horse's place of origin is believed to be in modern day Slovenia (though they are believed to have descended from Spain in the distant past). Lippizan is Slovenia's national symbol. Plus Lippizans are associated with the ‘Spanish Riding school' but the ‘Spanish Riding School' is situated in Vienna, Austria.
Character mistake: When Denzel is talking to the crew about upgrading to DEFCON 3, they say the last time was 32 1/2 years ago during the Cuban missile crisis of October 1962. The problem is that they both take place during October, meaning that the half year part is a mistake. (00:34:00)
Character mistake: More than once the crew of the submarine salute the Captain while uncovered in the hallways of the sub. Sailors never salute without their cover on.