Six high school friends, Johnny, Kitty, Matt, Simon, Zeke, and Deb, set out to celebrate their graduation by taking a trip to a remote lake. They plan to row to an island in the middle of the lake for a day of fun. While rowing across the expansive lake, they encounter an enormous, mysterious creature lurking beneath the water. The creature attacks their boat, causing chaos and leading to a desperate struggle for survival.

The group is stranded in the middle of the lake with no cell service and dwindling supplies. Tensions rise as they try to figure out how to escape or signal for help while avoiding the creature that continuously threatens them. Personal conflicts and secrets surface, further complicating their dire situation. The friends must decide whether to stay united or take drastic measures to save themselves. Their friendships and resolve are put to the ultimate test as they grapple with the terror that lies beneath the surface.