Socializing in the sauna: how do I know if someone starts a conversation to pass the time or if it’s interest, like platonic or romantic?

It’s kinda odd, I’m pretty good about determining if someone is interested or if someone is just talking ‘at’ me.

Weird thing is these guys who talk to me have the opportunity to do so when I’m swimming in the pool or at the machines (I don’t wear earbuds or headphones) and I happen to think it would be less weird if they wanted to talk then vs the sauna. I do read books but for whatever reason, that doesn’t seem to deter people from striking up conversation.