Two families join forces for a sailing holiday, but after their navigation equipment stops working, they find themselves separated and stranded on a mysterious island that doesn't seem to exist on any maps. The six kids have to work together to survive on the apparently deserted island, while their parents search for them. But, unknown to them, there are others nearby who are determined to keep the island's secret: an illegal drilling operation which threatens not only all wildlife on the island but the whole sea.