A young boy, Periwinkle escapes his mundane polluted surroundings when he ventures into a magical underwater environment. There he encounters many exotic sea creatures including Bun; a morphing Jellyfish who protects him against exposure to the water and Dorothy; a struggling sea turtle trapped in a net. After rescuing Dorothy things take a turn for the south when Bertha; a giant plastic octopus comes onto the scene. Bertha’s toxic presence and uncontrollable thrashing threaten to destroy the beautiful reef where the sea creatures live. Now it is up to Periwinkle and his new found friends to stop Bertha in her tracks and revert the sea back to its pristine state.