The Mediterranean concentrated targets, escorts, and aircraft in the same confined waters. Bioluminescent organisms could also illuminate the disturbance made by a moving submarine. An observer above the water might then see the boat's track even when the hull itself was submerged. Local environmental conditions could defeat concealment without any new sensor or weapon.
Notable Point · 27:51-28:27
Bioluminescence could betray a submerged submarine
Glowing marine organisms sometimes made a submarine's movement visible from the air in Mediterranean waters.