Just north of New Zealand's biggest city, tens of thousands of fish school meters from the beach in one of the world's first marine reserves. Inside the Goat Island Reserve giant snapper can live for eighty years and crayfish grow to weigh 8 kilos. Both feed on the thousands of sea urchins that graze the kelp forest, maintaining a delicately balanced ecosystem. Like many of the reserve's inhabitants, they entrust their larvae to the ocean currents - so how do they find their way back to the reef when they take on their adult form and settle down?