I'm in the flooded corridor, and I've no idea how to get onto that duct. I'm playing it on PC.
To get a better picture at where I am, please follow this link. That page contains the following paragraph:
The Abandoned Chamber can be confused, so follow these directions: From the entrance, head left, jump the gap, then proceed down the staircase (into the central structure), then up another set. Jump the gap and proceed through the door. Climb the ledges within, then grapple into the vent overhead.
I'm in the exact position (in the picture above) where I'm supposed to "grapple into the vent overhead." But that vent can't be grappled! And it is too high to be climbed. That's why I'm stuck.