The comedic trio from the original ice age are back as Sid, Manny, and Diego go on yet another pre-historic adventure. Instead of making their way to an arctic pass, this time they must escape the valley they live in as it becomes an ocean due to global warming.
Along the way they meet a few new friends, and one rather large one. Ellie, thought to be the only other mammoth besides Manny on earth, played by Queen Latifa; and two possum brothers who cause more trouble than they can afford. The dynamic group of characters experience all sorts of trouble and excitement as they near the end of the valley where a boat awaits to keep them safe during the flood.
Moments before they arrive, the ice dam breaks causing the flood, leaving the group stranded. the frantic squirrel from the original ice age, Scrat, causes a crevice to open up triggering a glacial split saving the group as well as opening a passage revealing several other mammoths thought to be extinct. The trio Manny, Sid, and Diego seems inseparable, and now includes 3 new welcome members.