Baker Dill (Matthew McConaughey) is a fishing boat captain leading tours off a tranquil, tropical enclave called Plymouth Island. His quiet life is shattered, however, when his ex-wife Karen (Anne Hathaway) tracks him down with a desperate plea for help. She begs Dill to save her - and their young son - from her new, violent husband (Jason Clarke) by taking him out to sea on a fishing excursion, only to throw him to the sharks and leave him for dead. Karen's appearance thrusts Dill back into a life he'd tried to forget, and as he struggles between right and wrong, his world is plunged into a new reality that may not be all that it seems.