One problem, Joe. Mark was talking about a river, with
strong current. Bart was talking about a harbor.


Joe wrote:
No kidding Doug, I'd never figured that out without your help, but the
same effect can be seen in a rivers movement and a harbors tide, you
may not beleive this but water moves in both harbors and rivers, and
shallows effect the surface in very similar ways.


I think relatively few harbors have *that* much current,
even at the most constricted part of the channel. And the
current's effect over a shoal will be masked by wind.

I know of one hazard due to current in many East Coast
inlets that I don't believe Mark mentioned, and that is
current going over a shoal from the channel... ie tending to
pull your vessel onto it. In fact, several NC inlets have
this effect strongly enough (on some tides) that they have
not only pulled boats aground, but also piled up sand over them.

It certianly is possible to notice the difference in waves
over a shoal but only when the waves are relatively high
compared to the water depth. Most harbors will very rarely
develop 2' waves which is what it will take to reveal a 6'
shoal. Big wakes help, if there happens to be one crossing
the shoal in question when you happen to be looking.

Reading the waters surface is a good skill but it doesn't
take the place of a chart and it sure ain't the same as on
Ol Man River IMHO.



Mark Twain had some
comments about this issue, too.


Care to share them?


The only one I can remember off the top of my head is: "The
difference between the right word, and almost the right
word, is the difference between lightning and the lightning
bug." -Mark Twain

DSK