"Submarines mainly rely on their ears to monitor the environment around them, but a range of advanced optronic sensors remain key to surveillance and attack roles that can only be carried out visually. Submarines are regularly seen as the ultimate stealthy naval asset, and any new technology that can facilitate covert missions is keenly pursued. The vessels are traditionally used to a clandestine life deep in the ocean, but the move away from Cold War operations and towards littoral warfare has meant they are being used increasingly as a surveillance tool to gather information in maritime security operations closer to the coast. Under this new remit, the ability to build a visual picture is more pertinent than it has ever been. Of course, strategic data can be gathered acoustically, but even high-quality data fails to surpass visual evidence as concrete, incriminating intelligence."