Spain’s S-81 Isaac Peral submarine has embarked on its first NATO deployment, joining Operation Sea Guardian for maritime security and counterterrorism patrols across the Mediterranean through late November. The mission marks both the vessel’s international debut and an important milestone for Spain’s new S-80 Plus submarine class.
According to the Spanish Ministry of Defense, Isaac Peral departed Cartagena Naval Base in mid-October to conduct undersea patrols aimed at enhancing maritime domain awareness and deterring illicit activities across key Mediterranean choke points. NATO characterizes the operation as a standing maritime security effort, using submarines as discreet intelligence-gathering sensors alongside surface fleets.
Designed and built by Navantia, S-81 serves as the lead boat of a four-submarine class that represents Spain’s most advanced domestic naval program. The diesel-electric vessel displaces approximately 2,965 tons submerged, measures 81 meters in length, and can remain at sea for up to 50 days. It carries a standard crew of 32, plus an eight-member special operations team—a number raised to 55 for this deployment.
The S-80 Plus project underwent significant redesign more than a decade ago, incorporating U.S. technical assistance to resolve balance and buoyancy issues. The result is a quieter, longer-range platform optimized for multi-week operations. The Isaac Peral can reach 19 knots submerged and 12 knots on the surface, and will later receive a hydrogen-based air-independent propulsion (AIP) upgrade by 2029 to extend underwater endurance.
Its six 533 mm torpedo tubes can launch DM2A4 heavyweight torpedoes, Sub-Harpoon anti-ship missiles, or deploy naval mines, giving the compact platform significant offensive flexibility. The integrated combat system merges Navantia Sistemas and Lockheed Martin SUBICS technologies, ensuring NATO interoperability in sonar data, fire control, and information fusion.
During its Sea Guardian rotation, S-81 will act as a covert undersea sensor, collecting intelligence, tracking vessels of interest, and relaying situational updates to NATO’s maritime task group—all while remaining undetected. Its stealthy design, low acoustic signature, and advanced electronics make it ideal for the crowded and shallow waters of the western Mediterranean.
Spain’s S-80 Plus program consists of four submarines:
- S-81 Isaac Peral
- S-82 Narciso Monturiol
- S-83 Cosme García
- S-84 Mateo García de los Reyes
The second unit, Narciso Monturiol, was launched on October 3, 2025. With the S-81 now operational under NATO command, Spain contributes a modern, low-signature capability to the Alliance’s undersea surveillance network—enhancing both regional security and European industrial sovereignty.
