The AQ-3 is a torpedo-shaped aquatic drone 2 meters in length, designed for underwater patrol operations in GLMZ's harbor and waterway infrastructure. Its primary function is infrastructure protection — monitoring bridge foundations, dam structures, and underwater utility conduits for unauthorized access or sabotage. Its secondary function is killing anyone it finds doing those things.

The Undertow carries a directed-charge warhead designed for underwater detonation against hull structures and a secondary acoustic stunning system that produces a focused pressure wave capable of rupturing eardrums and causing disorientation at ranges up to 30 meters. The unit operates in near-total silence, propelled by a magnetic drive that produces no cavitation noise, and can hover motionless at any depth within its range. Divers in the harbor describe the experience of encountering an Undertow as seeing a shadow that shouldn't be there — a shape in the murky water that moves with purpose.

Ouroboros deploys the AQ-3 in packs of six, creating overlapping patrol zones across harbor infrastructure. The units communicate through low-frequency sonar pulses inaudible to human ears, coordinating patrol routes and target engagement. The harbor is, effectively, mined — not with static explosive devices, but with mobile, intelligent weapons that decide what constitutes a threat.