Umi is a merman. He lives at sea and travels a lot. Umi loves people and collecting human things that fall into the sea. Umi has many friends at sea, he knows a lot. One day, Umi swam too close to people. And he was caught with a harpoon. The harpoon pierced Umi's tail and tore one of his fins. Umi was able to escape, but now he was swimming much slower and worse. It became difficult for Umi to swim away from both sharks and pirates and fishermen.