The CIA once built a giant ship under the cover story of deep-sea mining — when its real job was secretly raising a sunk Soviet submarine.

Project Azorian used the Glomar Explorer, publicly billed as a manganese-mining vessel financed by a reclusive billionaire, to try to lift a lost Soviet sub from miles down. When journalists later asked about it, the agency's refusal to 'confirm or deny' the story's existence gave rise to the now-standard phrase, the 'Glomar response.'