The smell...! When nuclear submarines are at sea they mostly remain submerged with a sealed atmosphere. Part of the atmosphere control system functions are to remove carbon dioxide (CO2), since a build-up of carbon dioxide can become fatal. To remove the carbon dioxide submarines use a chemical called amine. When amine is cool it absorbs carbon dioxide and when hot will release it. So the amine is cycled through a machine referred to as a CO2 Scrubber, which will alternately heat and cool the carbon dioxide and pushes the gas into the ocean, keeping the atmosphere breathable. This is a very effective system, with the downside being the amine imparts a rather "unique" smell into the atmosphere. Which ultimately permeates every part of the submarine interior including crew members clothing and even their skin. In addition to the amine smell, submarine crews are exposed to cooking odors, hydraulic oil vapors, diesel exhaust that isn't quite captured by the diesel exhaust system, inboard venting of the sanitary tanks, and the smell of a large number of closely confined people. The interiors become quite fragrant. Crew members become accustomed to it and after a while never notice it. But other people do.