The 2-Headed Shark's heads change size depending on water level and enemy.
When Anne and the professor are running from the shark and the collapsing island, they switch positions, from behind one another to in front of one another, continuously between cuts.
When the camera shows the atoll from the boat, it looks to be about half a mile to a mile distant. When the camera looks at the boat from shore, it's only 200 to 300 yards away.
Toward the end, when Cole is alone on the boat, sailing away, a man (it looks like one of the deck hands that was killed earlier) can be seen standing on the deck.
When the megamouth shark is being moved from the bow of the ship by Professor Babish, in the close-ups, the waves show the ship is clearly at a stand-still. While the far away shots show the ship never stopped going forward.
The shark is shown attacking people in waist-deep water, which should have beached it.
The first diver has no visible injuries or blood loss after being bitten.
When they are showing the gasoline barrel in the final scenes it clearly has a cardboard top (not to mention that they are trying to ignite it with a wet t-shirt)
In several attack scenes, the shark's teeth can be seen to be bending, folding or flopping about in a non-teeth-like manner.
There is one shot of the shark with it's mouth open , and the sunlight clearly shining through it's gills , showing that it's a fake / hollow prop .
The two people being attacked by the shark go from screaming near the surface of the water to being underwater back to the surface .
After the shark attacks the young people in the water and swims away , one of the heads is very noticeably missing .
There is a spelling mistake in the credits:
(Credit #4) The Production coordinator is spelled as Production "coordanator".
Just when the ending is going nowhere, there is a tsunami, then conveniently, their lost motorboat (which they didn't notice until now) appears.
Anne is alternately in front / behind Professor Babish as they're running down the path .
At minute 0:24, the person filming the two skiers is doing so with the camera lens still on the camera.
In a couple scenes shot in the boat's cabin, the legs of the steadicam operator are visible reflected in a piece of glass facing the rear doorway.
During a short bird eye view of the atoll if you look up you can clearly see the helicopter propellers in the shot.
In several scenes, channel markers can be seen. Channel markers don't exist on the high seas.
In some scenes you can see long strips of shoreline. The film was supposedly taking place next to a single atoll.
The atoll is not an atoll, it's an island despite the fact a character corrects another character on it being an atoll.
When the boats race to the Sea King, they end up going in the wrong direction.