Goofs

When the guy form the boat grabs Mia's arm he is kneeling on the left side of the ladder firmly on the boat. As the camera angle changes, he is standing on the ledge by the second step on the right side of the ladder.

When Mia and Sasha talk about Xibalba, the Mayan underworld, Mia explains that the name means "place of fear". in reality, Xibalba translates as "hidden place".

In one scene dust breaks their radio transmission. That it is not possible.

The blind and colorless fish makes a shrieking noise and scares the girls. Fish don't have vocal cords or even lungs.

All characters underwater somehow are in the same radio channel, yet they cannot hear each other until they get face to face.

When entering the Mayan sunken city, the characters pass through tunnels with straight angles supported by archways. The Mayans did not know how to build archways, so tunnels and corridors are characteristically triangular.

As the girls are trying to reach the exit cavern they are fighting a massive current to reach it. The water is surging so fast they have to crawl slowly through it while debris is moving sideways rapidly, but all the time their exhale bubbles are rising calmly straight up in the water.

Near the 22.00 mark, you can see a gap in the decor, at the bottom, which shows that they are in a pool and there's a cable on the ground. You can clearly see the cable and the reflection of light and water.

In one scene towards the end of the film, the girls are at the underwater window of the boat; however, in the next shot, they're at least 15ft away and swimming towards it.

Near the end of the film the girls squeeze through a tiny space and one clearly sees that in some shots the actresses are using small sidemount tanks for their actual breathing air when the characters in the film are only supposed to have one large backmounted scuba tank. It is clear that the sidemount tanks were used to shoot the scene safely, they just show too much in the final shots and are very easy to spot.

The brochure the family is holding at the beginning (The Great White Dive Company) has the word "there" printed on it when it should read "their".

After Mia has been pushed in the swimming pool, Sasha says that "no-one likes her". When Grant says to Sasha "That's a really nasty thing to say", his lips do not match the word "nasty". It is possible his original dialogue was swearing.

When Mia goes underwater to scout after hearing music, she isn't wearing her mask, therefore she wouldn't have been able to see clearly.