(At around 54 mins) Just before firing the GPS tag when Jonas is startled by the shark, the first scene after he surfaces shows his comm in the wrong ear. This is due to a flipped shot. In the background, the ship, which was behind Jonas on the left side, switches to the right side for that one shot.
(At around 1h 35 mins) During the final fight with the Meg, Jonas is wearing a full-face mask underwater when he stabs the shark. But when they breach the water, the mask is gone and Jonas only has a re-breather.
(at around 1h 35 mins) Toward the end of the movie when the Meg jumps out of the water with Jonas holding on, the shark falls into the water before him. When the camera angle changes, Jonas is already in the water and the shark falls next to him.
(At around 46 mins) When Suyin is running looking for her daughter in the station corridors, she is holding her jacket in different hands every time the camera angle changes.
Meiying's hair pin changes position between shots near the end of the movie.
Owing to the general lack of sunlight at deeper sea levels, the Meg should realistically not be able to see at all as it surfaces, since the greater volume of light up there is much more overwhelming than what it's been accustomed to for millions of years. The book gets this right and has the important reoccurring plot-point that the Meg only surfaces at night because the sunlight hurts its eyes.
(At around 31 mins) When Jonas is making his rapid descent in the submersible, he starts getting a nosebleed and the crew monitoring his vital signs are alarmed at the gas build-up in his bloodstream. He's in a pressurized vessel; the rate of descent would have no effect on him physically.
(At around 7 mins) The mother humpback makes "singing" vocalizations as the humans watch her with her calf. While female humpbacks do vocalize some sounds, only the males "sing".
Radios don't work under seawater, except for Extremely Low Frequency (ELF) radio. But ELF only allows transmission of a few letters per minute and needs a gigantic (country-sized) antenna for broadcasting. In short, none of the wireless submersible communications shown is possible.
Having supposedly evolved for two million years to live at a water depth of 11,000 meters and withstanding the gigantic water pressure down there, it would be impossible for the megalodon to simply surface without its inner organs rupturing and its metabolism failing rapidly. No deep-sea animals have ever survived in shallow depths for more than a few minutes.
Jason Statham's accent appears to wander between Cockney London, American, Australian and a bit of South African.
His accent is his own and it is doubtful he could alter it. Watch him in Parker trying to put on a Texas accent.
An actor's inability to perform a believable accent is not a mistake in the filmmaking process, it simply comes down to the skill of the actor. It's quite literally saying that bad acting is a character error. Additionally, the authenticity of an accent is a purely subjective opinion. If bad accents were considered goofs, countless movies would be guilty.
His accent is his own and it is doubtful he could alter it. Watch him in Parker trying to put on a Texas accent.
An actor's inability to perform a believable accent is not a mistake in the filmmaking process, it simply comes down to the skill of the actor. It's quite literally saying that bad acting is a character error. Additionally, the authenticity of an accent is a purely subjective opinion. If bad accents were considered goofs, countless movies would be guilty.
(At around 9 mins) When Morris asks what the Origin is diving in search of, Mac and Zhang brief him on the details of the project. While this provides exposition for the viewer, no business person would be stupid enough to invest $1.3 billion in a project without knowing what its purpose was.
(At around 42 mins) When the research team is in the conference room looking at the screen with information about the Megalodon, the text next to the picture of the jawbone repeats in the first and third paragraphs, starting with "Many tooth fossils from all over the globe..."
It appears that for the shots of the dorsal fin, the same one was used throughout the film, even though they were dealing with 2 different sharks.
(at around 37 mins) When Toshi says "Gomen na" after he closes the hatch, the subtitles say "(speaking Mandarin)". Toshi is Japanese as is what he said, which means "Sorry".
(At around 5 mins) An on-screen caption indicates that the Mana One research facility is 200 miles off the coast of China. It is also built above the Mariana Trench, at the bottom of which is the hidden sea where the Meg lives. The Mariana Trench is actually off the coast of Guam in the central Pacific, nearly 3000 miles from mainland China.
This film uses "Philippine Trench" and "Mariana Trench" interchangeably. They are thousands of miles apart.
Before the Meg attacks the beach, it appears to be swimming in shallow waters. Most of the beach goers seem to be quite far out into the open high water. It would be impossible for a shark of that size to swim around the shallow waters. It would be already visible to the beach goers to see the shark out of water, not underwater.
(At around 1h 3 mins) When the Meg chases Jonas and is caught by the cable attached to the ship, it can't reach him as he slowly paddles back underwater. Earlier the Meg easily pulled the entire ship backward, so it would have no trouble catching Jonas. Even sheer inertia would make sure Jonas was within reach of the monster fish.
Unless the Meg is a very fast learner, there is no reason that it would be attracted to whale songs (as there could be no whales in its home territory).
During the rescue below the thermocline, Jonas points out the shark is attracted to the light and for Suyin to turn off her lights, yet once he has the Evolution attached to the Origin, thus no longer needing his own lights on, he leaves them on, attracting the Meg. He seems to suddenly forget that he can turn his lights off, stopping the Meg from seeing him.
During the rescue, Toshi closes the Origin's hatch and pulls the lever separating the two subs. The Evolution's hatch is still open, which should flood it but doesn't.
It has supposedly been two million years since the last Meg sighting. Such a discovery would prompt the world's paleontologists, scientists, etc., to keep it alive as opposed to killing it. This is actually a major plot point in the novel.
(at around 26 mins) At one point Jonas threatens Heller stating that, since they're in international waters, he can assault him and get away with it. This is a common misconception. International waters are not lawless. Ships and ocean-based structures fall under the jurisdiction of and are subject to the laws of the country in which they are registered. Jonas would be held accountable for any crime committed at the research station the same way as if he committed it in the United States (assuming that's where it was registered.)
Toshi's Japanese accent goes from thick to non-existent and back again.
When Toshi is writing the letter to his wife, his writing is linear from left to right. Oriental language is usually written vertically from right to left.