How to get onto a duct in Batman Arkham Asylum from the flooded corridor [closed]
Solution 1:
This video shows how to grapple up to that vent. (Jump to the 4'20" mark to avoid seeing a couple Riddler challenge solutions.) Sometimes Batman's grapple gun can be kind of finicky, so try a bunch of different spots.
If that doesn't work, make sure you're using a legal copy of the game. According to this thread on Eidos' forums, it looks like the designers created intentional glitches in the game to combat piracy. These glitches go away when the game is licensed.