Hi Andrew, as you might have picked up it's all about the tide on the day. I would be looking for the edge where the current is forcing water onto it, rather than along it. Ideally a rock bar where the water is flowing up and over it.
Edges where the current is flowing along it, it is best to find a bommie that juts out a bit and breaks the general flow along the edge.
My 2 cents anyway.