The German U-boat Type XXI was one of the most advanced submarines developed during the Second World War. Known as the "Elektroboot", it represented a revolutionary leap in submarine design and set the stage for modern submarines that followed. Unlike earlier U-boats, which were primarily surface vessels that could submerge for short periods, the Type XXI was designed to operate mainly underwater. It featured a streamlined hull that reduced drag, allowing it to travel faster underwater than on the surface - a rare capability at the time. The boat could reach speeds of around 17 knots submerged, thanks to its powerful electric motors and advanced battery system. This gave it a major advantage in stealth and evasion. The Type XXI was also equipped with a snorkel, a device that allowed the diesel engines to operate while submerged at periscope depth, drawing in air and expelling exhaust without surfacing. This made the submarine much harder to detect by enemy aircraft and ships. In addition, its quiet-running motors and automated systems significantly reduced noise, making it more difficult to track with sonar. Another key innovation was the automated torpedo loading system. The Type XXI could reload its torpedo tubes in under 10 minutes, much faster than earlier models. It carried 23 torpedoes and had six bow tubes, allowing for rapid and repeated attacks without resurfacing. The onboard radar and sonar systems were also far superior to anything the Allies had encountered previously. However, despite its groundbreaking design, the Type XXI came too late to change the course of the war. Of the 118 units completed, only a few ever went on combat patrols, and none sank an enemy ship. Production was rushed, and many boats had mechanical issues due to sabotage, poor materials, or lack of testing. By the time the boats were operational, Germany was already on the brink of defeat. Still, the Type XXI had a lasting impact. After the war, both the United States and the Soviet Union studied captured examples and used the design as a foundation for their own submarine programs. The U.S. Navy's GUPPY program and early nuclear submarines, as well as Soviet designs like the Whiskey class, drew heavily from the Type XXI. Though it never had its moment in battle, the Type XXI changed the way navies thought about undersea warfare. It marked the true beginning of the modern submarine age - a machine built not just to dive, but to fight and survive while remaining hidden in the depths.