It's a bit out of my area (!), but for those of you who are down there, this may be of some interest/concern .
The following notes are from the Royal Institute of Navigation:
The proposals allow for only one navigational channel from the Harbour entrance to the bridge, which is some places less than 15 metres wide to the MLW spring tide line. I and many others believe this is not sufficient to cope with the traffic flow during periods of congestion, especially during periods of strong tidal flows coupled with strong winds. It would certainly not be enough space for a vessel with high windage and/or poor manoeuvring haracteristics to turn without risk of damage to itself or other vessels.
Furthermore, the current layout allows for several different routes throughout the harbour and this is particularly important in relation to access to the swing bridge so that if the bridge opening is delayed vessels waiting to proceed up river have the opportunity to circle around the harbour giving them the ability to maintain way and steerage. The proposed layout will prohibit this, and many harbour users can foresee serious accidents occuring with visiting yachts and commercial craft exiting their berths on the west side of the Harbour, thereby crossing the single main thoroughfare to the bridge.
It appears that the Harbour Commissioners scheme is based upon tidal flow information produced for them by Hyder Consulting, which recorded a maximum tidal flow adjacent to the swing bridge of less than 1 knot. Many harbour users believe that the tide here flows in excess of 3 knots during a spring ebb. I believe this report can be accessed via the Isle of Wight Planning Application website, under the "Fisherman's Quay" application, and the Tide Survey which was carried out in October, 2007 is attached in pdf format. The report is flawed with fundamental arithmetical errors and the misconception that the duration between mean HW spring and mean HW neap tides is only three days.