I came to understand this as the kobayashi maru shower. The two sliding doors had to be closed after you slithered through the super tiny opening. You couldn’t turn the water on first or it would shoot out the door. If you waited until you got in you wouldn’t know what temperature the water was going to be when you turned it on. If you did make a terrible mistake once you were in, the walls were so close that you couldn’t raise your arms to fend off the problem.