Errores

The Captain when entering the lagoon also breaks his own rules calling for silent running and then leaves the intercom on so everyone can hear him through out the boat. Not to mention he is using active sonar right below an enemy ship.

When Lt. Braden is under the dock, he hits his leg on something and rips his wet suit leg, exposing his knee. When he is swimming back to the boat, his wet suit leg is intact.

When "Lt. Braden" locks out of the submarine to swim to the Japanese island, his aqualung's 2-hose regulator is installed upside down on his diving tank. Normally, the 'horns' on this type of regulator, where the intake and exhaust hoses are installed, is installed so that they're facing up. In the water, and later, on the beach, the regulator is installed correctly.

When Lt. Braden is getting his final briefing from Cdr. Stevenson before leaving the sub, the compartment only has the two of them in it. Lt. Braden then turns to climb into the escape trunk and the compartment suddenly has many more men in it. Even if they had just entered, the narrowness of the hatch would have required them to enter one at a time making it impossible for them to suddenly be there.

When Braden steps onto the submarine, he salutes the rear of the boat, which is where the flag would be displayed; yet over his shoulder the flag can be seen rolled up and leaning against a cable. In the next shot, the flag is at the rear of the boat.

There are a lot of uniform errors, and, there is no way that the Navy would allow an ensign to remain for 15 years.

The Japanese are driving an American jeep.

It is not possible to weld underwater with an acetylene torch.

Despite wearing black clothing to avoid detection, when the navy diver proceeds to sneak onto the island, he would have been trained to blacken his face and hands so they don't shine, even during daytime, because remaining undetected is crucial for that mission. This practice was common for more covert American missions in WWII Pacific, as it still is today. Doing so would also minimize biting insects, which is a serious concern moving covertly in jungle environments. It is likely the face remained unblackened for visual purposes for the film, since faces are so essential to emotional human drama on film.

Alan Hale Jr.'s character Pat Malone is listed in the IMDb cast list as being of the rank of Lieutenant (Lt), whereas he is an Ensign, two ranks lower. There is a scene where Pat Malone shaves his beard after being promoted to Lieutenant.

The Aqua-Lung was developed by Emile Gagnan and Jacques-Yves Cousteau only in 1943; hence it was unavailable at the time the action took place (1942).

While it is true the Aqua-Lung was first used in 1943, IMDb guidance for Anachronisms states, "We allow a good deal of leeway with antique equipment and machinery as long as it is "of the period" - a 1943 variant of a military airplane in a movie set in 1942, for instance, will not qualify as a goof."

Braden exits the sub at 4:00 AM to swim to shore, 500 yards away. This should have taken no more than 30 minutes (about the same time it took him to return to the sub). Therefore, his arrival time would have been no later than 4:30 AM -- before sunrise. However, Braden steps ashore in broad daylight..

The Japanese pier holding gasoline shows barnacles on pier supports. After putting an incendiary device on top of the pier, Lt. J.G. Kenneth M. Braden's hand hits the barnacles causing them to wiggle, revealing they are nailed on plastic.

Malone goes to the commander and asks him if there is anything else to put in the night log. The commander says no. Then Malone asks about submerging at dawn. The Commander again says no. But this conversation takes place with a blue sky in the background. The choice of filters to darken the scene was a poor choice. Not only was the scene not darkened very well, the sky was a brilliant blue resulting in a "night time" scene appearing very much to be daytime with abundant sunlight for filming.

The opening title identifies the time period as 1942. When Lt. J.G. Kenneth M. Braden flies from San Diego to Honolulu, it is on a DC-4 or, in Navy terms, an R5D. These planes didn't enter Navy service until February 1943. Also it is shown in post-war colors with a red, white, and blue national markings, which also was post-war.

The Jeep that carries Lt(jg) Braden (James Garner) to the submarine is an M-38 that did not enter service until 1950.

The "Japanese" aircraft that attacks the submarine is a North American T-28 Trojan that did not enter service until the early 1960s.

Though the story begins in 1942, the transport that takes Braden to Pearl Harbor has US aircraft insignia that did not come about until after the Second World War. In 1942 there were two different insignia on US aircraft. The year started with the white star in a blue disc and a red disc (a red "meatball") in the middle of the star. But because the red "meatball" was similar to the red "meatball" on Japanese aircraft and could possibly confuse US service personnel, it was dropped in mid May, 1942. For the next year, US aircraft insignia was simply a blue disc with a white star in its middle. In June, 1943, the white bars were put on both sides of the blue disc. It was not until 1947 that red stripes were put in the middle of the white bars. This is what the air transport that took Braden to Pearl Harbor had on its wings, 5 years after the movie's setting.

The water barrel outside the Japanese steam room is clearly a western prop, with wide, rough staves and four iron bands. A traditional Japanese water barrel would have small smooth staves and hemp bands.

The underwater action is supposed to occur in the South Pacific, but the kelp (underwater vegetation) and fish are indigenous to Southern California, where the scenes were filmed.

Braden is taken in to the Lagoon where he leaves the sub. Yet he is shown coming up on the beach from the open ocean when he surfaces.

When Stevenson has his last-minute talk with Braden before his diving mission, he addresses Malone as "Ben" instead of "Pat".

While the sub is running on the surface, the radar unit gives trouble. Just before the radar technician pulls out the faulty radar display unit, he asks the control room "to send up a one-two-S-S-7." (This is an octal-base pentode vacuum tube (valve) used in RF and IF stages of a receiver.) No radar or radio technician would refer to it as a "one-two-S-S-7. In receiving tube parlance the first one or two numbers refer to the filament (heater) voltage which in this case is 12 volts. He should have asked for a "twelve-S-S-7".

(at around 1h 0 min) The Capt. of the sub gives the order to fire torpedo one. Only he has not given the order to open the outer door. The torpedo would damage and at some point blow up in the tube if he failed to open the outer door.

Lt. J.G. Kenneth M. Braden asks the submarine ensign why they keep red lights on. The navy diver already would know the red lights are used to preserve night vision.