Didn't see any sign when off coast of Brazil but did see my first one ever in Hells Gate in the East River @ NYC
when I went through during the "super moon " of last July. Maybe 10 meters( 30 feet) across . I could look right down into it ,just like a bath tub draining, but was not aware of its presence until right upon it since my cockpit
is already near water level. Houdini was making 10 kts SOG in this extreme flood tide and I entered at a tangent and just held on as my little craft was snapped120 degrees off course so quickly that i fell. I wouldn't want to repeat this experience and do not believe there was any danger
to my 10,000 lb boat, but a canoe ,kayak or dingy would surely have capsized and it would have been impossible to swim in those turbulent waters.
Lest I alarm
any readers here contemplating this route
,let me state that I have been through Hells Gate many times over the last 30 years and this was the only real whirlpool ever encountered. There is however a story (urban myth?) of a tug with a tow that was lost
here when these swirling waters pulled the tow ahead of the tug which then pulled the tug stern first so that she flooded and sank. Somebody please check on this and report back.
There is also a semi -permeant whirlpool in my home waters on the Hudson
River north of Kingston on the East side that I have always wanted to investigate. It is such a regular feature that it is marked as a feature on the NOAA charts
If any reader is now so intrigued by this phenomena they can search for a rather obscure short story by that famous navigator,Egdar Allen Poe of all people ,who expounds upon his theory on how to extricate oneself once one finds themselves in the big swirl.
.....................Love you all........................mike.................