Well, that seems the opposite of what I've learnt, whereas copper is used as a base layer upon which nickel can adhere better. But by no means I am an expert in this field, so I could be wrong. By the way, copper plating something that would be put into seawater doesn't sound a good idea to me, as seawater is terribly aggressive and a thin layer of copper wouldn't lasts much. Antifouling agents are based on copper (I) oxide (Cu2O, or cuprous oxide) which is dark red. While copper salts by themselves are relatively toxic for living ornganisms, in seawater copper likely converts into copper chloride oxides rather than cuprous oxides. The former are farily soluble in water while the latter are insuluble. This means the salts are dissolved and corrosion will progress quickly.