HL2 - Stuck on the Canal -1 reply

Hi: I am at the canal and on the ledge. I used the artilary gun but cannot find my way to the next level. Keep getting killed by artilary. Any help would be appreciated. Also, is there some site that provides hints as you go from level to level? Thanks. -CK

You're supposed to go back, and to the there's a passage through in one of the walls

(it's a while since I played that part, so I'm not exactly sure if this is correct)