A diesel-electric submarine is a type of military submarine that uses a combination of diesel engines and electric batteries for propulsion. When on the surface, the submarine runs on diesel engines, which charge the batteries. When submerged, it relies on these batteries for power, allowing for stealthy operations underwater. These submarines are known for their versatility and cost-effectiveness compared to nuclear submarines. They can operate at various depths and are often used for reconnaissance, anti-submarine warfare, and other naval missions. Their design allows for longer underwater endurance than traditional diesel submarines, making them valuable assets in modern naval fleets.