I had UHWM on my 14' Willies which is sold now. I believe the material bouyancy offsets the weight, and it is very slippery. But, when you hit a rock just right it still can stick in the riveted area. UHWM is also very expensive. Willies offers it on new boats as an option for $400 I think.

On my other boats I have always used Coat-It which is superior to Gluv-It. Coat-It is less expensive, just as slippery, weighs less and draws less water than UHWM. And it is replaceable. The only downside is that every year you have to turn your boat over and re-coat the bottom.

To each their own
Good luck!
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In the legend of King Arthur, the Fisher King was a renowned angler whose errant ways caused him to be struck dumb in the presence of the sacred chalice. I am no great fisherman, and a steelhead is not the covenant of Christ, but with each of these fish I am rendered speechless.