There's an underwater river right below the ledge they're standing on, and the next ledge is a bit too far to jump. Good thing there are two ways across: either swing across the ropes that hang midway across the chasm, or climb down, ford the river, and climb back up again. It looks climbable enough.

If you go by water, though, mind how long you're in it -- it's very, very hot, and there's something in the water that looks suspiciously like a giant octopus.