i've accepted this hunt for Sorbet, and went to the waterway but for the life of me i cannot get to the section where the mark actually is! only one door in storehouse 5 will open and its into the overflow cloaca, and any path from that i try to take will not let me down to the west sluice control where the mark is. what do i need to do?

oh and btw i don't need actual battling help to beat the white mousse, i'm plenty powerful for that.

thanks in advance!