5. USS Nautilus

The USS Nautilus was the world’s first nuclear-powered submarine. Until the Nautilus, submarines were powered by diesel engines that could not be used underwater. Subs could either expose themselves on the surface when using their diesels, or run submerged on batteries that had limited power. But a nuclear-powered submarine could spend its entire voyage submerged and hidden. In 1955, for her maiden voyage, the Nautilus traveled 1,100 nautical miles – the longest submerged cruise in history at that time.