Don't apologize for digressing, Dan. It is all very interesting.
Steve, it would be great if you could put the diagrams and vectors on this forum (or e-mail them to me if you can't).
However, I'm not sure how to use this knowledge to get me up the creek faster.
More questions:
Is there some rule of thumb for figuring out in advance whether or not it is even possible to get in against an outgoing tide, depending upon the relative speeds of the current and the wind? If the attempt is doomed from the outset, time would be better spent looking for a tow. Of course, the speed ability of the boat would also be a factor, I assume, so a Tornado would be able to get in with less wind than a Hobie Wave?
Also, concerning the current itself, I know the current is stronger in the middle of a channel than at the sides, but what happens with the current vis-a-vis depth? For instance, if the current is 3 knots on the surface of the water, is the speed incrementally less or greater at various depths below the surface? (Maybe this would depend partly on the shape of the bottom of the channel?)