Port Credit Marine Survey
& Yacht Delivery
|9. Reading The Water|
|I have taken hundreds of photographs of currents
and eddies trying to illustrate a few
the following points but I am not enough
of a photographer to do a good job
the subtleties of these with a digital
(or any other kind), but I do have
shots that may help along with a couple
diagrams. With some practice you should almost always
be able to sight the deeper water in
Whether it is deep enough is another
The river - Mark Twain once made a living as a Mississippi River pilot and the river pilots of today although backed up by many other methods still heavily rely on their local knowledge of a particular river and an understanding of river dynamics and how they affect underwater topography. I do not claim to be an expert in this field however I do remember high school geography classes on river formation and I am a fairly observant person. If I was really good at this I would be making $200k working 8 days a month as a river pilot but I do have a few tips. The key to successful river or inlet cruising is observation and continual learning.
River Basics -The chart at right shows the primary factor of concern to boaters.
|As a river bends, centrifugal force causes
the bulk of the current to scour a
channel on the outside of the curve.
The deeper water is almost always at the
outside of a bend. The slower moving
on the inside of the curve is more
affected by shore and bottom friction
causing back eddies which deposit silt
the downstream inside of the curve. This is complicated
somewhat by river currents being opposed
by tidal currents but is generally
The Yeocomico River shown below is a good example of this phenomena.
The above water topography also gives
to what may be under water. If there
high banks on one side of a river and
banks on the other, the high banks
been eroded by faster and therefore
water. The low sloping bank marked
dots continues about 75 yards into
where water is 2’ deep. The black dotted
line shows the path of the boat going
hard against the far high bank in 18’
water on the outside curve.
"X" Shows position of the boat in the photo
When traveling in 12’ of water with a light chop, a still patch probably indicates a shallow spot as the friction with the shoal slows the water down. When passing close by a shallow spot, the water accelerating around it may give your boat a little push to one side. If you over correct (natural reaction) you may run into the bank.
Photo 1. Section A shows moderately rough water therefore faster and deeper. Section B shows the transition area between deep & shallow where faster and slower water fight each other. Section C shows relatively still water indicating a shallow bank.
Photo 2. Same thing but more subtle in this shot.
Close observation of surface effects
go a long way to keeping you off the
Unlike the Bahamas or the keys, until you are well into Florida the water is largely opaque and the colour of the water tells you little about what’s under the surface.
The water here was so still and opaque that
without the wake of the distant boat
which passed us two full minutes before this
shot was taken) shown hitting a shoal
point (B) we may not have seen the bank.
Need a marine surveyor in Ontario... See this list of Every Marine Surveyor in Ontario