In winter, Great Lakes animals must deal with extreme temperatures. Divers explore the lakebed where a colossal ice sheet once ground into North America's bedrock, leaving five giant lakes when it melted. Each year the ice returns, challenging life. A powerful jet stream dip creates huge ice storms, the world's largest freshwater waves, and lake effect snow. Life has adapted. Otters frolic beneath Lake Huron's ice surface; giant freshwater cod sing and mate in the frigid waters; ravens outwit bald eagles and wolves, feeding on a deer; snow provides insulation for new-born black bears; the huge paws of a Canadian lynx help it move in deep snow; and the ultra-violet fur of flying squirrels deters predators. But some creatures are suffering due to the shorter, warmer winters. A rare wolverine is threatened by the warming climate and Great Lakes moose are declining in numbers. Ice and snow created North America's Great Lakes and its species have evolved to survive the harsh elements. In this warming world, the future of life in the Great Lakes will be shaped by one species - us.