The unrestricted zone is from just east of the derwenthaugh marina down to the site of the old dunston powerstation (just west of the coast staithes). I think it's around 2.5 miles long. There are no pontoons, a few ladders down off the jetty wall and one set of steps down from the small staithes there.
One problem you do have, depending on the tides is driftwood in the river, the further upstream you are however, the less of a problem it is.
You can also ski up at Newburn. there is a ski club there and a nice ramp for club members only though.
The day launch stuff is run by Powerhouse marine who are based at the marina, 0191 4140065