Children of the sea

As a child, Ruka saw a ghost in the water at the aquarium where her dad works and now feels drawn toward the aquarium. Ruka meets Umi and Sora, two mysterious boys who were raised by dugongs and hear the same calls from the sea the she does. Ruka's dad and the other adults who work at the aquarium are barely aware of what Ruka, Umi, and Sora are experiencing as the kids find themselves involved in the mysterious worldwide disappearance of the oceans' fish.