The water levels in the corridors constantly changes. Prior to their escaping from the moon pool area, the water in the corridor is above the doorway and deep enough for a partially-eaten body to float past the window. After the survivors somehow escape from the moon pool level, the survivors flee through the corridors where the water level has fallen to between waist-high and shoulder-high.
(at around 1h 6 mins) There are several mistakes when Derek and Josh are attacked. When the water came into the room, Derek jumps up onto the top bunk and the water fills the room up to the bottom of the bunk even though Josh is still shown as only being waist deep. After the water rises it doesn't go over the bunk. Later Derek uses the steel framed bunk as a raft.
(at around 49 mins) Sharks have no vocal cords, or any other method of making sound, but Bella's pups all shriek.
(at around 40 mins) The boat that struck the generator was not solid enough to have caused the damage it did to the generator or the generator's housing. No matter how fast or hard the sharks pushed the boat, it could not have caused the damage it did to the generator to cause it to short out or catch on fire.
(at around 39 mins) The fins of the sharks never rose high enough out of the water to be able to slice the mooring lines and cast the boat partially adrift.
Bull sharks only birth 1-3 pups at a time.
(at around 43 mins) When Josh is collecting samples from the sedated Bella, a closeup of her eye is seen with the pupil quite narrow. The sedatives should heavily dilate her pupils.
When Misty is undressing after jumping into the water to "rescue" Aaron, her clothes and hair are soaked, but her underwear is dry.