Originally Posted by MikeJohns
I've seen builders polyurethane sealant thinned with petrol and painted on a wooden boat and it has lasted very well. But not as an antifoulant.
All the "slick surface" antifoulings need a water velocity of over 15knots to self clean. Otherwise they foul.
I did see a very clean rudder and prop a month ago when inspecting a 70' commercial fishing boat. The owner had been given a bucket of a waterproof product called "ClearGlide lube" that's used in the oil industry here for protecting pipe threads and also apparently for coating cables in ducts so they can be pulled out in a few years.
He'd applied it around 6 months before to the prop and then to the rudder for a trial, both were spotless ! If you are interested in tough low friction waterproof coatings it might be worth looking at.