Lower Levels of Oxygen
Submarines have limited oxygen, which while safe, can be detrimental to your health. For example, it becomes more difficult for your body to heal if you’re injured when there’s less oxygen.
That said, if you happen to slice yourself while working on a submarine, you will definitely not be happy. Aside from the fact that your injury would constantly seep because it couldn’t heal properly, the reduced oxygen can also cause your energy levels to drop and induce mood swings.