Some years ago there were people using copper foil on the undersurface of the hull. I heard some boats had lasted over 10 years without being slipped and yet the hull was still clean.

This would of course be considerably cheaper than thicknesses of copper plate adhered to the hull, and I guess its possible to apply copper foil much as vinyl wrap is done, perhaps it could be electroplated onto some materials. Foils are typically 0.006"

I think stainless would be more problematic, stainless is generally avoided for submerged components of boats because it needs an amount of oxygen in its surrounds.