After a storm nearly destroys their beach house, Arion and his sister Maria go to the shore to collect shells. They chance upon a dolphin washed up on the beach, hopelessly entangled in a fish net. As the kids try to free the animal, to their surprise and delight the dolphin starts to speak. Delphis, it turns out, is a magic dolphin. In exchange for his freedom, he takes them on a world-encircling journey where they learn about beach erosion, sea level rise, plastic pollution and ultimately, what they must do to save their home from the rising sea.