Five friends (Nat, her boyfriend Tom, Milly, Tyler and Greg) are partying in Mexico for Spring Break on their last night. Nat goes to buy more beers and a beggar asks her for money. Noticing her noticing his legs, he tells her a great white chomped down on them. Her friends arrive and despite the man not being scary, they treat him poorly and he tells them to be careful.The next morning, to recover, they steal some jet skis and head out to sea. After a lot of mucking about, Greg and Nat's ski crashes into the other. Greg's leg gets broken and both jet skis are damaged with one sinking. After congregating on the remaining dead jet ski, they set Greg's leg and ponder their next move. When Nat tries to get phone signal on Milly's phone, she finds pictures of Milly and Tom among messages discussing an affair. In a bad mood, she fights Tom over it and loses the phone. Tom goes to recover it and somehow finds it on the sea bed.They realize they're drifting further from land and begin to panic. Tyler decides, as the strongest swimmer, that he'll go off in search of help. Shortly after he leaves, the group spot a great white fin heading towards them. The ski is knocked and they all go flying into the water. Nat's hair gets caught in Greg's watch and the remaining two watch in horror as Greg is attacked by the shark, dragging Nat down into the deep alongside him. Finally, she's able to break the watch and escape while Greg becomes shark food.Tyler is seen swimming and spies a boat. He begins yelling and trying to get the attention of the fisherman whose music is (naturally) too loud. Not too loud, though, to drown out Tyler's screams after the shark bites him. However, the fisherman is obviously dumb and takes his time looking for the source of the yells because by the time he looks in Tyler's direction, he's dead.Milly begins wondering what they'll do if Tyler gets eaten by a shark and Tom tells her to shut up.Nightfalls and they spot a red light in the distance. Realising it's a beacon, Nat goes to find help. However, instead she finds a mauled man in a life-jacket.The next morning, driftwood from the unfortunate victim's boat reaches them and they use wood to fashion ores and begin paddling. As Milly can't swim, Nat gets the life-jacket off the corpse and gives it to her. Inexplicably, the shark attacks and bites Tom. Bad CGI follows. Nat manages to stab it in the eye and it goes away. They realize they can't out paddle the shark and their only hope is to get the engine started. Unfortunately, it's under the seat and they'd need to get off the ski to open up. They devise a plan to stay safe while fixing the engine but the shark attacks again, sending all three in different directions. As Milly shrieks for help, Nat swims to her, but Tom, in the jaw of the great white comes between them and is launched into the air. Nat ops to save Tom first and gets him back to the ski. She attempts to save Milly but the shark gets her first, chomping her in half. Nat drops what's left of Milly into the ocean.Nat again sets about getting to the engine and snaps some rusty metal off the guard before getting into the engine box. Tom, from blood loss and dehydration is fading fast so Nat keeps him talking to keep him present. She notices a broken cable that needs some plastic tubing and sets about swimming to Milly's corpse to get the life-jacket back. As she's on her way back, the shark attacks and Nat uses the broken metal to defend herself.She appears before Tom and manages to get the tubing connected and the engine running. But the shark is faster than the ski and takes a bite out of the ski's hind quarters. As it starts to slow down, Tom slips off into the water and unwraps his wounds to draw the shark. Nat makes a half hearted plea to get him back on but she recognizes she's better off without him and leaves him to die, as she should.As she approaches land, shallow rocks begin giving her grief and tear into the ski, eventually throwing her off. In a final chase, she manages to escape the shark.and makes it to the shore where she cries and enjoys the sand. Somehow after two days without protection she's still milky white! Good for her.