Using a dynamic mix or archival footage, interviews with veterans, and dramatization, WAR AT SEA documents the role of the Royal Canadian Navy and merchant Navy in "The Battle of the Atlantic." Part I: U-Boats in the St. Lawrence tells of the little-knows "Battle of the St. Lawrence," when German U-boats boldly sank ships right on Canada's doorstep. The saga of the Canadian war at sea begins with the Corvettes - nicknamed "the cheap and nasties" by Winston Churchill. Their job was to keep open the vital supply lines between North America and Great Britain. The German submarine command was determined to cut these off and starve Britain into submission. Allied Naval Command, including Canada's Chief of Naval Staff, critically underestimated the seriousness of this threat. This is the story of the more than 100,000 heroic Canadians who were thrown into battle with minimum training and primitive equipment against a highly trained, technically sophisticated foe. Against all odds, they managed to bring convoy after convoy safely across the Atlantic.