The Surcouf, the world's largest submarine in 1934, vanished on the night of February 18–19, 1942, near the Panama Canal, leaving no trace that could be recovered or confirmed. At 110 meters long, the submarine was an engineering marvel, carrying up to 130 crew members, an amphibious aircraft, and artillery comparable to that of a surface warship. Its disappearance remains one of the greatest naval mysteries of World War II, with no conclusive evidence to explain what happened. Two unconfirmed theories suggest it may have collided with a cargo ship or been mistakenly attacked by an American aircraft, which could have mistaken the Surcouf for an enemy vessel. All 130 crew members perished, and the wreck, believed to rest at a depth of about 3,000 meters, has never been found. When the Surcouf entered service in 1934, it represented a groundbreaking innovation in naval design. It was a hybrid vessel capable of operating both on the surface and underwater, armed with powerful artillery and equipped with a small reconnaissance seaplane stored in a watertight hangar. After France's defeat in 1940, the Surcouf joined Free France and took part in the liberation of Saint-Pierre-et-Miquelon. It then underwent a major overhaul in the United States, completing its upgrades in late 1941. By early 1942, the submarine was en route to the Pacific, a mission that would ultimately end in its mysterious disappearance. The Surcouf had departed from Bermuda on February 12, 1942, heading toward the Panama Canal, a critical passage connecting the Atlantic and Pacific Oceans without going around the American continent. The submarine was navigating at night on the surface, with all lights turned off, making it difficult to detect. It disappeared from radar screens and was never seen again. Despite extensive search efforts, the wreck has not been located, resting at an estimated depth of 3,000 meters, about 100 kilometers north of the city of Colón, near the entrance to the Panama Canal. Despite advances in deep-sea exploration, the Surcouf remains one of the most elusive wrecks in history. Sonar scans and underwater expeditions have failed to locate it, leaving the mystery of its fate unresolved. Without a confirmed wreck site or conclusive evidence, theories about its disappearance persist. The Surcouf has become a symbol of the uncertainties and ambiguities of World War II, where military operations, limited visibility, and the pressures of war could have led to tragic misunderstandings between allies.