For more than 150 years, the Great Lakes have served as one of America's busiest commercial waterways, connecting the ports of the East Coast to the heartland of America. We think of them as flat, docile bodies of water, but these inland seas have more shipwrecks than the Bermuda Triangle and can produce waves that crest at 35 feet tall. In Great Lake Warriors, a maverick American tug boat company braves storms, ice, and the competition as they navigate and transport materials across one of the most dangerous bodies of water in history. The heavy raw materials that build America, like iron ore, are transported over the Great Lakes in giant barges, guided by tugs. Without tugs, commerce here grinds to a halt -- and so does the country. Our heroes work for a small tug company called Calumet River Fleeting. We'll follow them between October and January - the most treacherous time of the year.