A roll film negative. On board the submarine Sealion (1959) towards the end of a long refit at Portsmouth. The photographer is in the sound room on the starboard side of the main flat between 56¼ and 59¼ stations looking aft, to port and down showing sonar units against the aft bulkhead. The units in the aft port corner are for the French built AUUD.1B Type 197 sonar which has fin mounted hydrophones. In the inboard bulkhead is the compartment sliding door. A vertical format negative.