Iolo heads out to sea to look for Risso’s dolphins. Underwater, an artificial reef has formed from an old shipwreck. He finds roosting bats at an old priory, and dragonflies and beautiful rare plants on Anglesey’s fens. On the Alaw estuary, he gets a rare sight of Britain’s smallest bird of prey, the merlin, as well as Brent geese overwintering on Anglesey.