Ian and his sister Marina live on a beautiful tropical island with their Uncle Patrick, an old sailor who tells them wonderful stories and makes magical pictures with his pipe smoke. Among their friends are Jean-Sebastian, a great joke teller who can talk to the sea animals, Raoul the Koala Bear and Flem the living clock.

When the merry band meet Zoom the White Dolphin and his family, they get caught up in a series of exciting adventures as they explore caves, shipwrecks and the mysterious world beneath the waves.