Nazi Germany fought its war underwater as much as on land, and this episode uses ocean-floor mapping and CGI reconstructions to strip away the water and show what remains. Sunken U-boats, scuttled surface raiders, and cargo ships loaded with looted gold sit on the seabed as physical evidence, and marine archaeologists and historians read each wreck for what it reveals about German strategy. One thread follows the hunt for U-boats that slipped into South American ports after the surrender, feeding decades of rumor about escaped officers and hidden treasure. Another tracks a submarine base and the wreckage of ships sent to disrupt Allied supply lines across the Atlantic. Digital recreations rebuild vessels from sonar scans, letting the film show how each ship worked before it sank and how it ended up on the bottom. The result treats the ocean floor as an archive, piecing together operations that written records alone never fully explained.