Alex Low

12,000 feet down, life is erupting. Alvin, a deep-sea mechanized probe, makes a voyage some 12,000 feet underwater to explore the Azores, a constantly-erupting volcanic rift between Europe and North America.

From polar bears in the arctic tundra to black bears in the Northern Rockies, you'll see some of the most spectacular footage ever shot of these enterprising omnivores. Catch salmon with a group of hungry grizzlies on the McNeil River in Alaska. Crawl inside a den with a mother black bear and her cubs. Learn about the challenges facing each of these species as their habitat diminishes.