Navantia's shipyard in Cartagena has achieved a significant milestone by successfully installing a Hydrogen-based Air Independent Propulsion System (AIP) into an S80 class submarine. This groundbreaking technology, known as BEST (Bio-Ethanol Stealth Technology), enables the Spanish Navy's submarines to remain submerged for extended periods compared to conventional diesel-electric submarines. The AIP system does not rely on stored hydrogen but generates it on demand through a bioethanol reforming process, providing operational stealth and safety advantages. The system also reduces the need for visible snorkel manoeuvres, enhancing the submarine's undetectability and overall mission effectiveness. The completion of this installation marks a crucial advancement in the S-80 Programme, showcasing Spain's prowess in shipbuilding and naval technology. Navantia's AIP offers unique capabilities that give them a competitive edge in international submarine construction tenders. The system not only enhances the strategic autonomy and deterrence capability of the submarines but also ensures the safety of the crew by minimizing personnel requirements and improving operational efficiency. In a recent event attended by the Spanish National Armament Director, Admiral Aniceto Rosique Nieto, participants had the opportunity to witness the sophisticated AIP equipment, liquid oxygen, and bioethanol tanks installed in the S-83 Cosme García submarine. This demonstration highlighted the rigorous safety protocols and advanced construction techniques employed by Navantia in revolutionizing submarine technology. The successful integration of the Hydrogen propulsion system reaffirms Spain's position as a leader in military innovation and sustainable naval solutions.