The Indian Navy is set to enhance its submarine capabilities through a collaboration between Indian engineering giant Larsen & Toubro (L&T) and Spanish shipbuilder Navantia. The newly unveiled bioethanol stealth technology (BEST) offers the Indian Navy a cutting-edge Air-Independent Propulsion (AIP) system, providing submarines with the ability to remain submerged for extended periods compared to traditional diesel-electric submarines. By leveraging a bioethanol reforming process to generate hydrogen on demand, the AIP system eliminates the need for stored hydrogen, enhancing operational autonomy and crew safety. Navantia's AIP system, branded as BEST, utilizes a hydrogen-rich stream to power fuel cells for stealthy battery recharging while submerged, marking a significant technological advancement in submarine warfare. With a focus on tactical superiority and adaptability, the system allows for refueling at standard ports, eliminating the need for specialized infrastructure. The L&T-Navantia partnership aims to bid for India's Project 75 submarine acquisition, aligning with the Indian Navy's modernization goals and indigenization initiatives. Navantia's commitment to providing full technology transfer underscores their dedication to enhancing India's submarine fleet. The S-80 submarine series, operational with the Spanish Navy, showcases Navantia's technological expertise and readiness to offer advanced submarine capabilities to India.