A roll film negative. On board the submarine Sealion (1959) towards the end of a long refit at Portsmouth. The photographer is in the generator room below the main flat between 77 and 82 stations, this space being irreverently known as the snake pit. He is looking forward, to starboard and up into the forward starboard corner showing a lubricating oil filter unit in the foreground. An automatic emergency lantern is mounted on a pillar on the right. A vertical format negative.