Well done, Elizabeth! Williamson and Anderson turns... reminds me of my initial shiphandling training.

Something to do with Bernoulli's principle.....saw something recently about it which said that in reverse the bow is likely to get kicked off to the side

I totally agree with your explanation of prop-walk, John. 'Paddlewheel' and differential water density explanations are implausible because the moments are so small. The accuracy of the prop wash on the hull theory is reinforced, in my view, by the way that the degree of prop-walk varies with the underwater profile of the boat. As a generality, long-keeled boats with keel-hung rudders have a very large amount of underwater surface very near the prop and tend to have prodigious prop-walk. Medium keel boats, like Coric have less deadwood, so a bit less prop-walk. Fin and skeg boats have less material near the prop and hence modest prop-walk. Extreme fin keelers with spade rudders (eg Sunshine in our experience) have very little prop-walk. Of course, all of these theories totally fail when you are relying on more or less prop-walk in a difficult berth!

I am triggered by your theory on propwalk. It would be good to have some data as of different hull shapes? Never saw a credible explanation so far actually. Maybe in naval literature?