Arthur's fallen in enough holes that he's not particularly bothered by it, just a bit pressed (metaphorically and literally), so the joke doesn't hurt, but he does make a face about it.

When he gets the belt dangled for him - well, at least it's something, and he grabs it with both hands, half-wrapped it around one wrist to brace it.

"Got it-!" And he starts to pull, hoping to whatever god is listening that the stranger's properly anchored - Arthur's light, but still.

And lo and behold, it only takes a little bit of scrambling to get an elbow back over the edge, and to get hauled back up to solid ground again.