Secrets of the Aquarium

Marcus, the new curator, attempts a high-risk move for a problem shark to the top of the aquarium. Andrew builds a cave for a reclusive lobster, and star attraction Friday the turtle suffers a nasty bite from a mystery tankmate.

Marcus and Emma head to the Maldives on a rescue mission for an injured turtle. Back in Plymouth, Ian trains Zeus the zebra shark using a toy boat, and Andrew collects fresh seaweed for Larry the lobster.

Marcus installs a shark cage to allow visitors a close encounter, and a new octopus arrives from Portugal. Amelia has problems that threaten an ambitious project to replant the seagrass meadows.