Submerged signal ejector

A submerged signal ejector is a device used by submarines, similar to a torpedo tube. Although, instead of deploying weapons, it launches signal flares, smokes, distress buoys, SEPIRB, water temperature sensors and countermeasure decoys from the submarine.^[1][2][3][4] Signal ejectors can also send communication notes,^[4] as was done in the rescuing of the BAP Pacocha (SS-48) crew.^[5]

Submerged signal ejector on the USS Cavalla (SS-244)