"Perhaps a new one?"

Me and my friends were hanging out the other day at a creek next to a golf course, which we have deemed it "The Mysteriously Big Portion of Water," because we're retarded and can't remember the difference between a creek, a lake, a river, or a water fountain.
So we're hanging around and we see an old guy. We're just like, "This guy's gonna tell us to go away." But he sees us and says, "Perhaps a new one?"
He leaves, and we're just like... "What just happened?" We were wondering the crap out of what he just told us! "Perhaps a new one?" What's that supposed to mean? A new "what?" A new diaper change or brain transplant? A new child to freak out? What the crap does he mean?!