My boss and I have half joked that the next time I pull my boat to rehab the bottom, I should just spray it polyurea. It is strong and would certainly offer some protection if you hit some object. It's not at all practical to keep some aboard to seal a hull
puncture. Next time I'm testing one of my robots, I'll hand spray the outside of a pipe and drop it in the water
next to my boat to see how the marine
growth compares. There is nothing inherent to the chemistry that would repel marine
growth so I don't think you would be any better off that applying a ablative boat coat. But that's just a guess because I still need to test it.