8wt rod is fine. Overhaning blackberry bushes? Good! If they fish are feeding around them (they might not) make a fly that resembles a blackberry.
I've seen carp feeding on the bottom in relatively shallow water (3' deep) and about 10 feet away from shore. You have to be extra sneaky! they see EVERYTHING. Nymphs fished on the bottom catch fish. Especially if its a muddy bottom, dragging nymphs on the bottom is effective.
Good luck