U-513 was laid down at the Deutsche Werft shipyard in Hamburg on April 26, 1941, and commissioned on January 10, 1942. She was a Type IXC, the workhorse of Germany's long-range submarine fleet: 1,120 tons surfaced, armed with six torpedo tubes and 22 torpedoes, plus deck guns fore and aft. Her twin diesel engines could push her 13,450 nautical miles at 10 knots on the surface, far enough to reach the shipping lanes off North and South America. Submerged, her electric motors gave her a range of just 63 nautical miles at 4 knots. The crew of 53 lived in conditions that would test anyone's endurance: cramped quarters threaded between machinery, torpedoes stored in every available space, fresh air a memory within hours of diving. Her first commander, Korvettenkapitan Rolf Ruggeberg, took her through eight months of training before her first war patrol.

U-513's first patrol began on August 7, 1942, when she slipped out of Kiel and headed into the Atlantic through the gap between Iceland and the Faroe Islands. Off Newfoundland, in Conception Bay near Bell Island, she scored her first kills on September 5. She made port at Lorient, in occupied France, on October 22. Her second and third patrols took her into the mid-Atlantic, but the hunting was poor, and she returned empty-handed both times. By spring 1943, the Battle of the Atlantic was turning against Germany. Allied air cover was closing the mid-ocean gap, and U-boat losses were mounting. In May 1943, Ruggeberg was replaced by Guggenberger, a decorated veteran who had already sunk an aircraft carrier. His assignment to U-513 reflected the Kriegsmarine's growing desperation: experienced commanders sent to boats whose odds of survival were shrinking by the month.

U-513 departed Lorient on May 18, 1943, heading for the Brazilian coast, where Allied shipping remained less protected than in the North Atlantic. The gamble paid off initially. In five attacks near the coast of Santa Catarina and Parana, she sank four ships and damaged a fifth. But on July 19, 1943, southeast of Sao Francisco do Sul, a Martin PBM Mariner flying boat from U.S. Navy Patrol Squadron VP-74, piloted by Lieutenant (jg) Roy S. Whitcomb, caught the submarine on or near the surface. The aircraft, nicknamed "The Nickel Boat" by its crew, dropped depth charges. U-513 went down fast. Of her 53 men, 46 died in the attack or in the water afterward. Captain Guggenberger was among the seven who survived. He spent the rest of the war as a prisoner, and he lived until 1988. The men who died with U-513 were mostly young conscripts, sailors who had little say in the war their government waged.

For decades, U-513 was one of roughly a dozen German submarines known to lie somewhere off the Brazilian coast, their exact positions lost. In 2003, the Schurmann family, a well-known Brazilian sailing family based in Florianopolis, began searching. It took nine years of research and two years of seagoing expeditions aboard a sailboat before they found her on July 14, 2011, resting at a depth of 130 meters, about 85 kilometers east of Florianopolis. Side-scan sonar images confirmed the discovery. A dive in 2012 produced the first photographs and video of the wreck, showing the submarine largely intact on the ocean floor. In 2014, the Smithsonian Channel aired a documentary called "The Ghost of U-513," weaving together wartime footage with footage from the wreck site and details from Guggenberger's postwar life. The film treats the story with the gravity it deserves: young men on both sides of a terrible war, most of them never coming home.

The wreck of U-513 lies in waters that appear calm and featureless from above. There is no marker, no buoy, nothing on the surface to suggest that 46 men are entombed below. The submarine is a war grave, one of over 700 U-boats lost during World War II, each carrying its own crew of fathers, sons, and brothers. The Allied merchant sailors and naval personnel who died when U-513's torpedoes struck their ships deserve the same remembrance. War at sea was brutal and impersonal: a torpedo in the dark, a depth charge from the sky. The men on both sides were caught in a conflict whose scale dwarfed any individual. U-513 is a reminder that the ocean keeps its secrets for a long time, and that behind every hull number is a roster of names.