The plot of this movie centers on two sisters, Kate and Lisa, who go on vacation in Mexico. In search of thrills, Kate convinces her sister to go with her in an underwater cage and take a look at some great white sharks. The cage breaks open, and the girls find themselves 47 meters deep in the ocean with a reserve of oxygen that will last one hour, yet the shore is two hours away. All around them are the most dangerous predators on Earth.