In article ,
"Ed Huntress" wrote:

Ok. "Oceangoing barges" sound like a possibility -- well out in the ocean.
Around here, the edge of the mid-Atlantic Continental Shelf it pretty far
out, and the waters of the shelf are pretty shallow. I don't know *how*
shallow they have to be to build up those big waves.

Pop down to the library and check out "Giving Good Weight" by John
McPhee, which includes an article (circa 1975) detailing the engineering
of a little project that was to be sited off the coast of NJ. I guess
you can also get it straight from the source (via web) if you are a paid
up New Yorker subscriber.

--
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