On board the Type 12 general purpose frigate Plymouth (1959) alongside the south side of number 3 basin in Chatham Dockyard at the end of a modernization which commenced in August 1966. The ship is berthed starboard side to the quay. The photographer is in the sonar control room between 35 and 39 stations on the starboard side of 1 deck looking forward and to port showing two sonar control positions against the forward bulkhead, identified by the photographer as the "C.O.2 panel". Against the port bulkhead by the side of the open door are an automatic emergency lantern, a CO² fire extinguisher, an echo injector, remote control units for the H.O.20 (type 177) and H.O.15 (type 170B) domes and some light switches. A vertical format negative.