This is a screenshot from my DM-Aquarium level. This shows the door and a wrench. One of the things I like to do when creating a level is to work a subtle story into them. The tool box (not pictured) and wrench were placed near a removed grate (also not pictured here) to help convey the idea that someone might have been here to do maintenance recently. Faint handprints are shown on the door as if someone else was desperate to get out.