Navantia's shipyard in Cartagena achieved a remarkable feat by completing the installation of a third-generation Hydrogen-based Air Independent Propulsion System (AIP) in an S80 class submarine, a first in naval history. The innovative AIP technology, known as BEST (Bio-Ethanol Stealth Technology), revolutionizes submarine capabilities by enabling battery recharging while submerged, eliminating the need for detectable snorkel recharging maneuvers. This advancement signifies a major milestone in the S-80 program, offering the Spanish Navy prolonged underwater endurance compared to traditional diesel-electric submarines. The event, attended by the Spanish National Armament Director, Admiral Aniceto Rosique Nieto, highlighted the strategic importance of this technological leap for Navantia and the national defense industry. The AIP system's bioethanol reforming process produces a Hydrogen-rich stream, combined with pure Oxygen, to power the fuel cell stealthily. Navantia's AIP stands out for its on-demand hydrogen generation, enhancing safety, autonomy, and deterrence capabilities. The installation showcased in the S-83 Cosme García submarine's Section 3 demonstrated the complexity and precision of the AIP equipment, liquid oxygen and bioethanol tanks, and supporting systems. This achievement not only enhances the operational effectiveness of Spanish submarines but also positions Navantia as a leader in advanced naval technology and submarine construction on the global stage.