Well know is the short answer cos 1 it silted up in Roman times and 2 some pilock built a weir across it. So I'm afraid you cant go to Chester any more
On Saturday, I saw a small fishing vessel making its way along the Dee from the old Dee Bridge towards Queensferry. When I was at school (all those years ago) in Chester, there used to be a few more small fishing vessels moored on the Dee on the other side of the Old Dee Bridge from the weir. I assumed that the Dee was navigable from Chester to the Iris Sea
The River Dee is navigable as far as Chester, it is tide dependent though. I am a member of Deeside waterski Club, we Waterski from Connahs Quay upstream 2 hours either side of high tide. We also cruise the Dee estuary towards the sea, Hilbre island being a favouite destination.
The channels are marked by the Normal Red/Green buoys from the sea ward approaches into Mostyn Docks. From Mostyn Docks to Flint the centre of the channel is marked by red/white striped buoys. From Flint to Connahs Quay the normal Red/green are used again. From Connahs quat to chester the River is much narrower, we rarely go much further up than Saltney but we can go as far as the Wier at Chester. Although the wier can be crossed on a spring tide it is dangerous and may be forbidden. There is access to the canal system through a lock about 2 miles before the wier.
Mooring in the estuary is limited, most of it either dries or is very shallow at low tide. There are several fishing boats moored, some of which dry out on mud banks.
If you want to make a trip up the river let me know, I will try to aanswer any questions you may have.