Marine Antifoul

Hard antifoul stays put — best for racers, high-speed power, and trailered boats that need a hull you can scrub. Ablative wears slowly off, constantly exposing fresh biocide — better for slower cruisers and longer gaps between haul-outs.

Yes if the existing coat is sound and the same chemistry. If you're switching from hard to ablative or vice versa, you need a barrier coat between them — otherwise the new paint won't bond properly and you'll see chunks coming off within a season.