Goofs

When Trent grows older and changes actors for the second time, the mole above his lip appears to be gone for a few shots. It is back with the next growth spurt/actor change.

Mid-size Sedan wears white sneakers that are clean throughout the movie, even though he's walking on a wet and sandy beach. When he's first talking to Maddox alone, in a wide shot, they are extremely dirty with wet sand, but moments later they are clean as new again. This happens a second time later in the movie.

When the difficulty of swimming around the coral is explained, the waves hitting the coral are much larger and more intense than the waves hitting the beach in spite of being close to each other.

After Chrystal fell unconscious and Maddox picked her up, while Kara is giving birth, there is a long uncut shot in which Sedan is nowhere to be seen. In the next shot, he is sitting just behind Kara, having appeared out of nowhere.

Rust does not poison the blood, as stated by Prisca. It can contain bacteria causing tetanus, which can lead to death by causing violent muscular spasms, but still not poisoning the blood.

During the breakfast scene, one cannot recover so fast from a (grand mal) seizure, especially being so alert, orientated and seemingly having a recollection of what happened ("twisting my neck").

The kids obviously outgrow their clothes instantly. For the daughter, it is explained that the mother conveniently brought an extra swimsuit of hers that she is able to wear. However, she is supposedly 16-18 at that point and definitely not the same size nor body shape like the mother. Yet it fits perfectly. Furthermore, at the end of the film when they're in their 50's, the same swimsuit still fits perfectly.

Accents of the characters vary throughout their life stages.

However, bad or inconsistent accents are a matter of an actor's skill and not a mistake on the part of the filmmakers. Considering the parts of the children were played by up to four actors each, it shouldn't be surprising that they couldn't align their accents perfectly.

The victims always have a fire burning on the beach. There is never any evidence of trees or driftwood to fuel a fire. However, characters are seen breaking apart the picnic baskets and talking about ripping empty pages from a found notebook, and the furniture brought with them slowly disappears, implying that they mostly (or entirely) burn items that they either find or brought with them.

Mid-Sized Sedan tells the group that his nose has been bleeding all day, but earlier in the movie, when he is on the beach with the girl who has MS, his nose is not bleeding. However, it is made clear by the shot of the van at the edge of the path and the sunrise over the water that he and the girl just got there, meaning the more noticeable effects of the beach haven't quite kicked in yet.

The nurse tells the surgeon to proceed again to the incision, asking him to do an oblique one. The first and second incisions are (logically) vertical and not oblique.

(at 17:48) Guy's mouth is not moving when he says, "I wanted to tell you something".

When they remove the tumor from Prisca, many characters put their hands into the incision. The characters do not wash their hands before touching the open incision. Later in the film, Charles is infected by a cut from a rusty knife. Following this logic, Prisca's incision should have become infected and caused sepsis, killing her.

There is no reason why Prisca's growing tumor would make her unconscious and, above all, why its removal would make her come back to consciousness.

It is explained that trying to leave the beach by the same path they entered causes blackouts from moving too quickly from one speed to another. If this were true, nobody would be able to get to the beach in the first place without experiencing the same effect.

Just minutes after the blackouts are explained, a character suggests trying to swim around the side of the cove. However, given the previous explanation, this too should result in the characters blacking out.

The actors playing Maddox at age 11 and at age 16 have different eye colors, while the eyes of Maddox as an adult go back to matching the 11 year old's color.

Rufus Sewell's character is English, yet the two things he chooses to compare the tumour to are a canteloupe and a softball. Maybe the first thing that might spring to an American screenwriter's mind, but almost the last things that would spring to an English person's mind.

After Patricia (Nikki Amuka-Bird) suffers her final seizure, the actress can be seen blinking normally from a distant camera shot.

(at 40:36) Charles, a senior surgeon, is holding his scalpel the wrong way.

(at 3:51) When the resort manager's nephew, Idlib, is introducing himself to the kids at the candy bar in the resort lobby, he mispronounces the word "conch" as rhyming with the word "launch. Someone from that region of the world would have pronounced it to rhyme with the word "honk".