riverman wrote:


I think if you were actually trapped in a hole with sharp enough edges to
keep you in, you would be underwater and tossed around so much that you
would have no idea which way 'down' was, let alone how to crawl along the
bottom.

That's correct. Spatial disorientation would be but one facet of the
experience that makes a low-head tailwater hydraulic a "drowning
machine". Visibility is bad to non-existent, bubbles go in all
directions, and the current is quite deceptive. I know a guy who went
diving in a similar current, looking for lost anchors. He did this and
several similar crazy things in his younger years, and is quite lucky to
have survived many of them. He's the only person I know who was in such
a current and lived to talk about it, he had SCUBA gear and advanced
training, he was quite impressed with the power of the hydraulic and
says he couldn't see how anyone without all the equipment could have
gotten out of it.

Our Dive/Rescue team had one of these hydraulics in our jurisdiction and
we used to really worry about a potential rescue or recovery there until
the Army Corps of Engineers solved our problem by rebuilding the
structure in question to eliminate the low-head dam.