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.
Visible crew/equipment: When Captain Dodge is sitting down to talk to Lake, you see the boom mic follow him down.
Visible crew/equipment: When Dodge Say's "Good ole Graham" you can see the mic on top of the screen.
Continuity mistake: During the final chase scene, Captain Dodge says that it's overcast, and they surface. The first shot of the Stingray shows a hazy day. When the Orlando surfaces afterwards, it's clearly that one piece of stock footage of a Los Angeles-class submarine surfacing - not only is it sunny, but the ship shoots up from an emergency fast rise. After that, the shots of the Stingray in pursuit, and that of the torpedoes hitting the target ship, show it to be sunny rather than overcast. [It's not just stock footage of any old submarine surfacing. It is in fact the shot of the submarine in Tom Clancy's The Hunt For Red October surfacing - exactly the same footage. Some kind of in-joke, perhaps?]
Continuity mistake: Capt. Dodge (Kelsey Grammer) is on the deck of the sub and is sending a crewman up a ladder to attach a lamp onto the periscope. To attach it, he uses duct tape. However, when they show him climbing, the duct tape is still in Dodge's hand. Then, a second later, it is magically in the crewman's hand.
Continuity mistake: At 1:20:35, when Dodge gives the order to "ready torpedo tubes one and two", both tubes are already showing "ready to fire" in the panel above Dodge's shoulder.
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.
Visible crew/equipment: When Stapanak is running to the engine room, the camera equipment at the bottom of the screen is visible.
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.
Audio problem: When Dodge and Jackson go outside to put the spotlight on the periscope, Jackson climbs up. He sings the Army theme, be all you can be. You hear Dodge say that's the army not the navy, but if you look at him when he says this, he doesn't even open his mouth.
Continuity mistake: When Dodge is in his room talking to Lt. Lake, he throws the towel on his bunk which can be seen in the mirror. A few seconds later back on Dodge the towel is now gone from the bunk.
Factual error: Stepanik is introduced in the crew boarding scene as an Engineman First Class, however in the homecoming scene, his uniform insignia is that of a Machinist's Mate First Class.
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.
Visible crew/equipment: When Howard is starting the engine, he's stepping over the dolly track for the camera rig.
Factual error: On the type of submarine Dodge is commanding, you must climb up to the conning tower to use the periscope. The periscope is not accessible inside the sub itself.
Continuity mistake: When Grammer is welcoming his new crew on board, between the time the first crewman has walked up the gangplank and Grammer is talking to the second and receiving his papers and telling him to get on board, you can see that a third has already boarded and the number of envelopes held by the ensign has jumped from one to three.
Continuity mistake: When Grammer is being taken by launch out to see his sub for the first time, you see between shots that he's going two different directions at different times of day. As they cut back and forth, one set of footage is a live shot, the other is against a screen. The end of the scene is a shot taken either in early morning or late afternoon whereas the preceding were more at midday.
Continuity mistake: When the Admiral asks Dodge how he likes his new boat, the pencil holder on the admiral's desk has three pencils lined up. After Dodge says, "It's a complete piece of..." the pencils have moved.
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.