I reckon the best way to see that whole area is to do a kayak trip down the river from Tocumwal to Barmah. Their are plenty of places to camp all along the river although you might need to paddle a km or two in sections as the river edge can be very steep and inaccessible. Its about 140km in river distance and takes about 3-4 days to paddle. The only gotcha is that if you have one car, the car-shuffle at the start is a bit of a hassle. You drop your kayak in Tocumwal, drive to Barmah and park then get back to the start at Tocumwal via public transport. Its only 80km by road from Barmah to Tocumwal but the only bus goes via Shepparton where you kill some hours before you can get the bus back to Tocumwal. It takes nearly a whole day to do the car shuffle. You could try hitching back to Tocumwal from Barmah I suppose.
Alternatively you can hire kayaks from
Gondwana Canoe Hire and he'll drive you to Tocumwal I believe.