Sisters Lisa (Mandy Moore, 'This is Us') and Kate (Claire Holt, 'The Originals') become trapped at the bottom of the ocean when a diving expedition to observe sharks goes horribly wrong. When the cable attaching the cage sinks to the bottom of the ocean, the sisters must figure out a way to get back to safety battling injuries, lack of oxygen, and worst of all, bloodthirsty, great white sharks.