Was everyone a volunteer?

Traditionally, everyone aboard a U. S. submarine was a volunteer. That has almost always been the case. The exception was early in WW2 when the submarine force needed to expand quickly. Some sub sailors at that time didn’t remember when they volunteered. (We like to say that they didn’t back up quickly enough when volunteers were requested or that they were “voluntold.”)

However, if you didn’t want to be on a submarine, you didn’t have to. Sub crews didn’t really want someone aboard if he wasn’t comfortable there. Sailors can always request to “non-vol”, even if he volunteered in the first place. Being at sea in such close quarters and submerged for so much time can be very different from just a training dive or two. It might be much more uncomfortable than the sailor imagined. The Navy can always find another place for a quality, competent sailor to serve.