Son of a Diddley!  You've done what I'd been trying to wrap my brain around for a while.  The only drawback I see is doing curved shores, and possibly adding foam (unless you go heavy post render.  I did something similar for church benches, but didn't think to apply it to water terrains.  (slaps forehead).  Gonna have to figure out  how to use this soon.  Hmmmmm ideas percolating.  Now you've done it. ;c)

 

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