He clearly doesn't understand what they've gone through. Robin has no sympathy--in fact, he smirks and makes a mental note to find out who Seth put on his team, since they're apparently both smart and funny.

"Lake? A few hours of walking. Plus the hour to make it up to the surface. Why?"

Robin will realize, later, that he shouldn't have mentioned the lake because of some potential logistical nightmares. But he hasn't realized it yet.

Vincent perks up at the question, though, tilting his head to listen more intently.