Continuity mistake: When Nancy is surfboarding, she is going to ride her last wave for the day. When she is waiting for her last wave, the ocean appears to be calm, but when it cuts to the very far 3rd person view a big wave pops up on the screen. When it cuts back the wave has disappeared.
Continuity mistake: In the movie, it's Nancy's left leg that is injured. When she dives into the water to swim through the jellyfish, suddenly it's her right leg that is injured. (01:03:45)
Continuity mistake: When Nancy returns to shore after doing her first surf, she goes to eat an apple. The first angle shows Nancy eating the apple with the core on top of the apple, in the next cut, the core is on the side of the apple, meaning the apple turned between shots.
Continuity mistake: Blake Lively's lips are chapped when the two surfers return the next day. When they are killed she gets the Go Pro and begins filming her message, her lips are no longer chapped.
Chosen answer: A shark tooth.
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