Rose and her mother, Alma, set out on a much-anticipated trip with Alma's new boyfriend, Derek. Although Rose is reluctant to accompany them, feeling like a third wheel, she ultimately agrees under her mother's enthusiastic insistence. Upon their first encounter, Rose senses that Derek is trying excessively hard to impress, while her mother is already quite taken with him. The trio embarks on a getaway in the vast, open sea, free from external distractions. However, Rose's apprehensions spike, particularly due to her fear of the ocean and discomfort with the proposed plan.
As the trip unfolds, a series of unexpected events leads to a budding rapport among them, revealing more about Derek's past; once a police officer, he now works as a security consultant. While exploring the cabin, Rose stumbles upon an AR-15 rifle and various pistols, igniting her curiosity to learn how to handle such weaponry. One fateful night, as Rose sleeps, she is jolted out of her dreams by disturbing noises from the deck. Venturing outside, she witnesses a fierce altercation between Derek and a group of men, culminating in a horrific tragedy where Alma loses her life, and Derek suffers a gunshot wound. In the chaos, these men attempt to set the boat ablaze, leaving the vessel in disarray. Miraculously, Rose manages to extinguish the flames and salvages what she can to survive.
Dealing with the aftermath of the fire, Rose finds clothes aboard the boat to cover her mother's body, hoping to give her a proper farewell should she make it back to land. The jib is entirely ruined, leaving her adrift in the ocean, grasping for survival. Suddenly, she discovers Derek, who has fallen into the water after being shot in the hand. She helps him back onto the deck and seeks his guidance on how to navigate their perilous situation. He instructs her to hoist the spare jib, and as they set sail, the wind and currents work in their favor. Rose discovers pictures of the attackers in the cabin, leading her to question Derek's loyalty, yet he remains her only tether to survival.
Their desperate fate leads them to an island, but soon they realize it's uninhabited and devoid of hope. Derek, wishing to sail further, decides they must sleep on the island for the night. After some revelations about Derek's entanglements with criminal elements, he recognizes that Rose knows too much, leading him to consider taking her life to protect his secrets. Displaying instinctive resourcefulness, she escapes into the jungle overnight. The next day, as she dashes towards their boat, Derek fires at her but slips and injures himself in the process. In a twist of desperation, he solicits her help, hoping to bargain with the Captain, a man with a reputation for preying on young women.
Disregarding his pleas, Rose throws a stone at him and departs, leaving him behind without the EPIRB. He falsely claims it is inoperable, but Rose knows better. Climbing back into the boat, she cuts her ties with Derek and focuses on her survival, even as the vessel begins to leak. She transfers to a lifeboat, but in her attempts to keep Alma’s body with her, she loses it to the depths of the ocean, leaving her devastated.
One bright morning, she spots a ship in the distance and frantically signals with her flashlight, but the ship fails to notice her due to the blinding sunlight. That night, a speedboat approaches her lifeboat, offering what seems like salvation, but she quickly realizes she is brought just yards away from the man who indirectly caused her mother’s death—the Captain. Understanding the gravity of her situation, Rose formulates a clever plan; knowing that the Captain would prefer to speak with her privately, she tricks him into falling into her trap. In a moment of sheer bravery, she knocks him unconscious, eliminating the looming threat.
With the ship now in chaos, Rose utilizes her shooting skills and survival instincts to take down the ship's crew one by one in a battle for her life. Ultimately, she confronts Derek once again. He has activated the EPIRB, revealing that he had already lined up a deal with the Captain to ensure his safety, but undeterred, Rose fights back with all she has. In a climactic struggle, she kills Derek, putting an end to his vicious pursuit of her life.
In the aftermath, the remaining survivors on the ship gather on deck and guide Rose towards safety, where she faces questioning from Agent Richard Friedman, who treats her with respect and admiration. Although Rose grieves the loss of her mother at sea, she emerges from this harrowing experience having saved numerous young girls, sending them back to their families as a testament to her indomitable spirit and will to survive against overwhelming odds.
