No, maybe not a surprise, but it did count as trying to get himself killed, that's what. Childermass lucked out in never having to meet the Gentleman directly, but he knows enough after the fact to know he'd rather Strange not call that creature into the carnival just to see if he could. And if not that one, then one similar.

But since he can't actually give Strange that direct a warning without further explanation, he'll just have to resign himself to hoping Strange never succeeds beyond annoying their coworkers. So, he shakes his head and returns to watching the scene in the water unfold.

"Of all the magic you could be trying on a whim, that is one I would prefer you let be for now, that's all," is really all he can say to that. It's not like he can actually stop Strange. Luckily, they won't be stuck on this topic forever, since something is happening at the meeting again.

That something looks like it might be an argument.