The AIP Submarine, or Air-Independent Propulsion Submarine, is a type of underwater vessel that can operate without surfacing for extended periods. This technology allows submarines to remain submerged longer than traditional diesel-electric submarines, which need to surface to recharge their batteries. AIP systems enhance stealth and operational capabilities, making them valuable for naval forces. AIP submarines utilize various technologies, such as fuel cells or stirling engines, to generate power while underwater. Countries like Sweden and Germany have developed successful AIP submarine models, which are increasingly adopted by navies around the world for their strategic advantages in modern warfare.