There are gases in mines, does that make you a little suspicious about stories that come from miners and whatever they might see, or think they see, deep underground?
Sailors and miners tend to be very superstitious people, working in risky places so deep underground or so far away floating on top of such deep water. It’s no surprise they come up with stories. Some people just like to scare each other too. See what they can get started… So do you believe everything you hear from miners, or sailors?