When Knox rejects the possibility that a Diesel-powered contact could be a submarine, he ignores the fact that the US Navy is the only navy in the world with an all-nuclear submarine fleet and frequently exercises with allied navies.
In one of the scenes, the Executive Officer calls LCDR Dodge "Commander". While the "Lieutenant" modifier is often omitted from lieutenant commander (or lieutenant colonel, for that matter), this is considered insulting in context, as LCDR Dodge was the Commanding Officer (CO) of the Boat, his correct title would have been "Skipper" or "Captain".
The Diesels on the Balao class boats did not connect directly, or through a transmission, to the screws. Rather, they powered generators, which charged batteries and ran the electric motors which did power the screws. Therefore, thinning the fuel-air mix, as CPO Howard does by adding whiskey in the final chase sequence, would not affect the RPMs available to the screws, even if it did slightly increase the power being generated by the engines.
At the end of the movie, Jackson is seen in formation with hair growth on his chin. Since it was shaved throughout the movie, he obviously did not have a "no shave" chit (as offered by the Navy for some medical reasons). Therefore, this growth would have been unauthorized.
When Cmdr. Dodge looks through the periscope before surfacing for the final attack, he says that the low clouds will hide them from aircraft. But once they surface, all the action takes place under clear blue skies.
When the Stingray is shown moving under the SS Denali the stand for the bow running lights, which should only be used when the sub is surfaced, is clearly visible. But when the Stingray surfaces for its torpedo run it shows no stand.
Sylvesterson was the first sailor picked to board the boat, but when Sylvesterson walks up the plank when boarding the boat, RJ Jackson is seen walking behind Dodge, not Sylvesterson. Where did RJ Jackson come from?
The sonar screen shown as the Stingray begins its torpedo run shows the same 'picture' as it does when the blockading vessels begin pinging before the Stingray hides under the Denali, even though the Dodge states that they are past all the ships and only the Orlando was near.
In the opening scene when Captain Knox gets up out of his chair to congratulate Dodge on his promotion, Dodge is clearly seen folding up his orders to shake Knox's hand. As he turns to walk out of the Captain's cabin, the orders are unfolded in his hand again.
When attacking Norfolk, Virginia, mountains can clearly be seen in the background. This region of Virginia has no visible mountains. As seen in the Filming Locations these hills are in the San Francisco Bay Area.
The golf course at the Naval Submarine Base of Groton, CT is north, or past, the sub base when coming in from Long Island Sound. The USS Orlando would have to have gone past the base and turned around in the narrow Thames River in order for the boat to be facing south and Lt. Cmdr. to take his golf shot aft of the sail.
Both the SS-number and the name are inaccurate for this design of submarine. The true SS-161 was a 4th-group 'S'-class boat (originally numbered as the 'S-50') built in 1920-21, and had been scrapped by 1932. The true 'USS Stingray' was a 'Salmon'-class submarine with the number SS-186. It was constructed in 1937-38, served and survived WWII, and was scrapped in 1946.
When the 'Stingray' passes between the two propellers of the tanker in its attempt to sneak into Norfolk, the propellers are shown to be at a level approximately half-way down the hull of the 'Stingray'. However, the 'Stingray' was said to be a WWII-vintage 'Balao'-class submarine and the distance from bottom of keel to top of the conning tower was something like 60 feet. This would mean that the propellers were suspended at least thirty feet below the hull of the tanker, which is completely contrary to modern ship design.
When Dodge asks for the surface picture prior to hiding beneath the Denali, Sonar says there are 5 Destroyers, 3 Frigates and the Denali. After that point, in the shots of the surface ships conducting the search for Stingray, all of the ships are Ticonderoga class Cruisers.
At the start of the film we see Cmdr Dodge playing his golf shot at the rear of the submarine's sail when the Orlando's Skipper calls down from the top of it. This is not possible because the only area where a person can stand when at the top of the sail is on the bridge, which is a further 20 feet forward at the front of the sail. There is no possible way to move from the front to the back without walking on top of it.
RAdm. Yancy Graham says, "He's gone AWOL with U.S. government property". AWOL, Absent With Out Leave is Army terminology. The Naval term is UA, which is Unauthorized Absence. However the producers felt the audience would recognize the meaning of "AWOL" but not "UA".
Lt. Cmdr. Dodge has had a bizarre career, as rank is concerned, in the Navy. He is clearly a mustang (noncommissioned officer who, after an OCS course, receives a commission), as after 20 years (according to his conversation with Cmdr. Knox) he is only a Lieutenant Commander (equivalent to a Major in ground/air forces). Despite this, he appears to be approximately the same age as Cmdr. Knox - who perhaps is another mustang. On top of that, "the Murmansk brushing incident" is stated to be both three years ago and while he was an ensign. It is also mentioned as an (understandable) obstacle to promotion, but Dodge has been promoted three grades in as many years since - clearly somewhat faster than the average officer should expect promotion.
During the initial dive of the SS-161 Stingray, the sub is tilted due to a air pocket. When viewing cast during this scene, some are angled the same as the ship, indication that the only thing tilted was the camera.