OK, sorry to take a while to reply. Some thoughts on tides and resonance:
Yes, harbours that are enclosed can have a resonant frequency, and I'm sure that can modify the tidal dynamics. There's a formula to work that out, what I need is the length and width of the harbour. It might be tricky because it's a really funny shape which doesn't even approximate a rectangle. Give me some time on that one. (I don't feel like solving the differential equations again when I know the info is in a book on my desk at the university!)
Regarding direction of the tide: Tides are actually very long-wavelength waves known as Kelvin waves. They travel with the coast on their right in the NH (which means on the left in the SH). Looks like this one should be travelling East to West.
The best I can do on short notice for St. John's Harbour (which is practically rectangular and I just marked an assignment where the students figured out the period of one of the modes of vibration), much more so than Poole Harbour) is
http://makeashorterlink.com/?H2F7213C, if anyone's interested.
Here's a much better map, courtesy of the Port Authority:
http://www.sjpa.com/images/Facilities/HarMap1.jpg
