A camera team uses advanced technology to penetrate the bizarre worlds of these icy waters, finding sunken medieval trees and ghostly wrecks.
A circus lion resists captivity, open water swimmers get a surprise visit from a pair of whales, and a dog is left on the wrong side of a door.
Alison and Donald head to Ohio, where lax laws have led to a thriving exotic animal trade, and visit a shelter overrun with deadly predators.
The falling temperature brings in some serious work for Michelle, as people rush to get their pets checked out before they're snowed in.
Dogs and humans share a rare social bond, but how do they really feel about us? Dr Brian Hare's games help people understand canine companions.