Hi,
if you want a bit of estuarine paddling on the lower Huon down near Dover, find -43.24813, 147.05451 on google maps.
There is a sort of boat ramp there, only used by locals, and you could camp overnight right beside the water and not be in any body's way. No amenities of course.
If you wanted a park for the night you could try the Dover Tourist park -43.314303, 147.023784 it is carrying distance to the water and the bay has some nice islands to paddle around.
You can check the tides for the area
here, it looks like you will have a low tide in the mornings and high tide after lunch. You might want to plan the direction of travel and return with that in mind. You will be able to see the tide times for the Monday in 24 hours time, they don't go far into the future.
Southport has some interesting waters, you can go into a lagoon from -43.446733, 146.958065 and there is a huge car parking area near by - could stealth camp there, but there is a caravan in Southport near one of the pubs at -43.42412, 146.97298
I have not used it, just found it on Google.
cheers