One of the regulars on an email list I belong to just posted this:

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The local coast guard came down to a boat which had hit a rock with a
can of foam-in-place. If you can slow the leak down somehow you can
fire that into the bilge or wherever and it will hold the water back
long enough for you to get somewhere. It is tenaciously gooey. I'm
planning on putting a can onboard.
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