It's June - winter in South Africa, and Martine and her grandmother are enjoying a cold but beautiful walk along the beach when they find a stranded, dying dolphin. Martine uses her gift of healing to help it back to the ocean but it's only the latest in a series of inexplicable beachings of dolphins and whales - and the start of a brand new adventure for Martine.
After a last stolen midnight ride on her beloved white giraffe, Jemmy, Martine's class is off on an amazing school trip to the islands of Mozambique to witness the legendary 'Sardine Run'. It's a trip that goes drastically wrong and Martine, with close friend Ben, finds herself swimming in shark-infested waters, marooned on an uninhabited island and suddenly at the centre of mysterious submarine goings-on as she tries to save a pod of 100 dolphins from certain death.