I bought a boat
a few years back that had Eco-Clad's previous product, Copper Clad. It came with a 10-year warranty that was transferable from the previous owner. After about two years, I saw a good bit of growth. Called the company and they re-applied it. No charge. There was some slime perhaps three years after that, but no hard growth.
I've talked with these people at the boat
shows. If I had a boat that I knew I was going to keep for several years, I'd consider it.