Sink a Pearson Ensign?
 

Yes. I didn't actually see it go down. I was racing on our Ensign on
a protected bay on Lake Ontario in about 20-25 knots in the late '70's
when one of our crew informed us that the competition had "sunk". We
looked aft and lo and behold it was true. Nothing but the mast was
left above the water. Apparently they had fouled a jib sheet when
tacking and been knocked down far enough to flood the cockpit. There
was some speculation that they might have reomoved some of the
floatation from the boat to make it a bit lighter, but they denined
this and there was no clear evidence of it when the boat was
re-floated.

--Tom.