If such a signal ever goes out, then the Submarine Parachute Assistance Group (SPAG) deploys.

Part of the Royal Navy, the SPAG specializes in the recovery of submariners. There are several jobs within the SPAG, such as medics, engineers, and submarine escape specialists — but all members are proficient in first aid, escape-and-recovery techniques and submarine, surface-to-air and ship-to-shore communications.

SPAG teams are on constant alert. In the event that a Royal Navy or foreign submarine requires their expertise, they can be underway in less than six hours.