Factual error: When the submarine rises in the waters of Norfolk and you see Norfolk in the background, there is one blatant problem. There are NO mountains in Norfolk. Most of Norfolk, Virginia, is below sea level.
Factual error: In the final chase, Orlando surfaces to chase Stingray. WWII subs are considerably faster on the surface, but modern Los Angeles class subs are designed to spend 99% of the time underwater. Orlando must travel slower on the surface as her aft rudders are out of the water, decreasing her stability. On the surface, the greater the speed, the more difficult she is to steer. Her speed and handling on the surface would be greatly reduced. There's no way she would have surfaced to chase Stingray, as it would actually make it more difficult to catch her.
Factual error: On the type of submarine Dodge commands, you must climb up one level to the conning tower to use the periscope. The periscope is not accessible inside the control room.
Factual error: In the opening credits, when you see a submarine (presumably the Orlando) passing underneath a bridge, the sub is going south, away from the base, seeing as the base pictured is the Naval Submarine Base in Groton, CT. The sub is supposedly returning from being under the ice cap, according to Dodge in another scene, therefore, it's going the wrong way.
Factual error: Most uniforms in this movie are worn incorrectly. Between wearing belts incorrectly, not wearing ribbons on dress uniform (shore patrol), female hair regulations, shoes, and having ribbons in the wrong order it's like they didn't even try.
Factual error: It is said in the film that the Stingray is a Balao class submarine. The Stingray was actually a Salmon class submarine, and likely called a Balao class because the USS Pampanito, which stood in for the Stingray in the film, was a Balao class. Source: http://uboat.net/allies/warships/ship/2938.html. (00:05:45)
Factual error: After the Stingray does the simulated attack in Charleston Harbor she launches a red flare. A green flare is used to indicate a "gotcha" in an exercise and would have been used there. A red flare indicates the submarine is in trouble and will attempt to surface.
Factual error: The uniform that LT Lake wears in the last scene is wrong. The Service Dress White Uniform for women includes a white shirt and black necktie. There is no way the Navy lets anyone walk around with visible cleavage. This has nothing to do with the myth that it's illegal to portray actual military uniforms, which is entirely untrue.