Scrat's endless pursuit of the elusive acorn triggers a cataclysmic event, resulting in the Earth's continents beginning to shift and break apart. The consequences are sudden and severe for Manny, Sid, and Diego, the beloved trio of prehistoric animals. Manny is separated from his wife and daughter when a massive chunk of land cracks away, setting them adrift on a treacherous chunk of ice. The continental shift poses a relentless series of dangers, and the friends are propelled on an epic maritime adventure, navigating the high seas on their unstable ice raft. With the landscape altering dramatically around them, Manny insists on the importance of reuniting with his family, and the group pledges to do whatever it takes to return home.

Along the way, the trio encounters a diverse band of pirates led by the fearsome ape Captain Gutt, who tries to pressgang them into his crew. As the threats escalate, the bonds between Manny, Sid, and Diego are tested. Sid faces additional family drama when his long-lost, cantankerous Granny joins the group, bringing her own unpredictable antics. The motley crew must overcome natural disasters, battle pirate foes, and navigate interpersonal dynamics to survive and stay on course. Despite their disparate personalities and the chaos surrounding them, the friends discover the power of teamwork and resilience amid the vast and changing seas.