Blooper

Opening scenes are live action shots of a British-type destroyer with British markings. Model sequences show a US type destroyer.

When new medical officer Lt. Commander Chester Potter and reporter Ben Munceford are dropped aboard the ship by helicopter it is a British frigate with the identification number F-159 on the stern. Chief Hospitalman McKinley later refers to the ship's identification as DLG 113. Bow shots of the model used for shots photographed in a tank also show the ID as 113.

At the beginning, when Potter and Munceford are lowered from the helicopter to the ship, in long shots the sky is clear, but in closeups, there are clouds in the background.

As the movie opens, the ship is the British destroyer HMS Wakeful (hull number F-159), but after the doctor and journalist are delivered, the vessel (as a model) becomes the US Navy's DLG-113, a fictional vessel apparently intended to represent a Farragut-class destroyer. Interiors are obviously a Royal Navy ship.

The studio prop ASROC (Anti-Submarine ROCket) control panel which is manned by ENS Ralston (James MacArthur) jumps (in the last few minutes) from the CIC (Combat Information Center) to the bridge.

Some believe that the U.S. Navy of the mid-1960s was segregated and Black sailors could serve only in limited categories, which is not true. The U.S. military was desegregated in 1947 by President Harry S. Truman and Navy rates (jobs) were open on a race-free basis.

The modelers used a FARRAGUT Class ship for the fictitious BEDFORD. US Navy officers with the rank of Commander (O-5) are Commanding Officers (CO) of FARRAGUT class Frigates/ Destroyer Leaders. Eric Finlander (Richard Widmark) wore the rank of Captain (O-6). Note: in the Navy, the term "Captain" represents rank O-6 and the title for the Commanding Officer of a ship. Those holding the rank of Captain include officers in the Supply, Medical, Dental, Judge Advocate, Chaplain, Nurse, and other Staff Corps as well those in the SEALS, Aviation, & Submarine warfare communities. To complicate the issue, generally, ship COs who hold the rank of Lieutenant Commander (O-4) are often called "Skipper" instead of "Captain", and Captains (the rank) who Command Squadrons use the title Commodore. So, not all ship COs earned the rank of Captain, not all officers with rank of Captain are ship COs, not all COs are called Captain, and some Captains are called Commodores.

Photojournalist Ben Munceford is shown with both Nikon and Pentax 35mm cameras around his neck at the same time. A real photographer might use two cameras with different angle lens, but he would not use cameras with mutually exclusive mounting systems, in this case bayonet and screw mount. This would prevent lens interchangeability on the two camera bodies and flexibility with any additional lenses available.

Most of the "inaccuracies" of the film's plot and events follow the novel itself, including the ASROC firing. The explanation of those has been given by author Mark Rascovich in his note to the novel, "Some of the techniques and equipment ... have been deliberately obscured."

Ensign Ralston (James MacArthur) could not fire the ASROC by himself. Any nuclear weapon requires two people to coordinate the launch, including ASROCs.

At the beginning, when Ben Munceford (Sidney Poitier) and Lt. Cmdr. Chester Potter (Martin Balsam) are being lowered from the helicopter, their hands are bare. However, their stunt doubles are wearing white gloves.

When Ben Munceford is interviewing Capt. Eric Finlander, who is sitting in front of a porthole window, it is apparent that the view outside the window is a set painting.

While at General Quarters (battle stations), some officers of the USS Bedford are shown wearing dress blue uniforms. In the mid-1960s, both officers and chiefs wore khaki uniforms while at sea.

The 24-hour clock on the bridge was originally manufactured for the U.S. Army Air Force by Seth Thomas. However, that information on the face has been covered up with a label that says "United States Navy". U.S. Navy clocks by Seth Thomas had a black face with white numerals and hands.

This film was made in 1965 and was a "present tense" story. Several sailors are labeled as "seaman first class" and "seaman second class". Those designations were dropped following WWII. The correct designations for sailors of this level would be "Seaman Apprentice" and "Seaman".

When a chunk of an iceberg falls off in front of the ship, the wire guiding it is visible.

Captian Finlander calls a Russian expert among his crew to the bridge to translate his message to the Soviet submarine demanding it surface and identify itself. He dictates, Seaman 1st Class Williams (Paul Carson) translates. The message is very brusque and demanding. The instant Finlander is done, he dismisses Williams (without waiting to see if any message is received in return from the Soviets, which was a possible outcome regardless whether the vessel stayed submerged or surfaced).

Lt. Cmdr. Chester Potter, when promoting his ideas for an improved crew to Capt. Eric Finlander, pronounces "amino" acids as "am-ih-no" acids (vs. "a-mee-no"). A medical doctor would know the correct pronunciation.

Near the end, sonar operator Queffle arrives on the ship's bridge in a state of shock and exhaustion. The medical officer is called to examine him. The doctor quickly checks Queffle's eyeballs, apparently to view the condition of his pupils, but he performs this exam with Queffle's eyeglasses still in place. The glasses would have distorted the doctors view of the pupils somewhat, possibly resulting in an incorrect diagnosis.

After shooting down the doctor's plans for the crew, Captain Finlander lowers a brace holding books on a shelf to hand a few of them to the doctor. He doesn't return the brace to its secure position to hold the books - even as they are going to General Quarters status.

Finlander tells Munceford and Potter that he has three Russian language experts on board, but in the radio room shortly afterward there are five men present, of whom four certainly, and the fifth probably, are clearly fluent in Russian.

The German officer is using British Barr and Stroud naval binoculars, which would not be expected on board an American ship.