The corpse of a gigantic creature washes up in the Pacific Ocean. Scientists want to preserve it, believing it to be a prehistoric organism, but it is already beginning to rot. They also observe that patches of its skin are transparent.
A boy has come to see the discovery, having felt compelled to go there for reasons he can't explain. He has been terrified of fish since a visit to an aquarium when he was a child. Since then, he has been plagued by dreams of floating in the sea, surrounded by giant, grotesque species unlike anything that exists today.
The boy gets talking to a young woman named Mie, who had also come down to the scene. Her fiancé Tadashi was lost at sea many years ago as one of the passengers of a ferry which sank, but none of the people on board were ever found. Mie has begun to have dreams that she is Tadashi, floating next to people she doesn't notice; terrifying sea creatures surround her, kept at bay by an invisible wall. The boy realizes this is the exact same dream he has had.
Meanwhile, the people looking at the creature discover that something is still moving inside it. Peering through the transparent patches of skin, they discover what appear to be hundreds and hundreds of people trapped inside the creature. Although they are in what should be its intestine, they haven't been digested. The people are retrieved from inside the creature's stomach, revealed to be everyone who disappeared in the ferry crash, including Tadashi. Although they are still alive, they have become zombie-like parasites living off the creature, and all are declared insane. The boy, remembering his dream, wonders what horrors they could have seen in the sea, through the creature's transparent skin.