Technical Paper— Directional passive acoustic monitoring systems (JASCO Applied Sciences’ OceanObserver™) were deployed near Lisbon, Portugal, in September 2025 aboard five Slocum™ G3 (Teledyne Webb Research) and six SeaExplorer™ (ALSEAMAR) ocean gliders in support of NATO’s Robotic Experimentation and Prototyping with Maritime Unmanned Systems (REPMUS) 2025 exercise. Each glider was equipped with a spatial array of hydrophones enabling the gliders to make directional acoustic detections and to measure ambient sound conditions. The localization of acoustic signals was demonstrated by comparing simultaneous directional detections from a swarm (or squad) of the gliders with the known tracks of underwater mobile sound sources. Further, each glider was fitted with a conductivity-temperature-depth (CTD) measuring instrument, allowing the gliders to measure sound speed profiles in situ. These profiles were used for modelling acoustic propagation loss, which was combined with the known sound source levels and ambient sound measurements to predict detection ranges. The glider data, detections, ambient sound, and CTD measurements were telemetered to shore via Iridium and displayed in PAMlab™ (JASCO Applied Science) and SeaSuite™ (Blue Ocean Marine Tech Systems) and GLIMPSE™ (ALSEAMAR). Validated detections of targets were sent to various REPMUS command and control systems displaying the Common Operating Picture. The underwater gliders proved to be valuable in supporting the Anti-Submarine Warfare (ASW) team and Rapid Environmental Assessment (REA) team at REPMUS 25. The ability of this swarm of gliders to both detect and localize the targets of interest was successfully demonstrated. The potential for underwater gliders to provide persistent maritime surveillance and ‘Early Warning & Indicating’ was proven. Valuable data for related ASW Research & Development were collected during the REPMUS 25 vignettes.