Series that explores, amongst other things, how the growth of phytoplankton along the coastal waters of Alaska and British Columbia attracts a vast array of marine life to feast on billions of herring. Humpback whales migrating from Hawaii, as well as Steller sea lions, dolphins and killer whales make the long and arduous journey toward the abundant fish, risking malnutrition and attacks from predators along the way - all in the name of some decent grub. Another fascinating documentary from the BBC and the incredibly spritely-for-his-age David Attenborough, this is the last in the current series. But in saying that, we're sure RTE will be regurgitating it once again soon enough.