For Cranberry, did you come in via Hall's Road or the Lynde Shores parking lot?
If coming in by Hall's Road, park at the second area that's closest to the lake. The path will split south towards the lake, and then heading east along the lake, there's a few places where you can look into the marsh.
From Lynde Shores, if you follow the bird feeder trail, there's a path south towards the marsh, and there's a lookout platform there as well.