If it is an enviromental reason, some workboats use red oxide primer, (a soft paint) with talc added. When this is painted on thick in multiple coats, it gives a similar effect to the ablative(self scrubbing) bottom paints. Of course, this will still "litter" the marine enviroment with paint and talc.
If it is for some other reason, if you could list your "case" for giving up on anti-fouling, perhaps we could better understand your requirements.
We used to use something called 'water-tank paint' below the water line on traditional steel river craft. Its black, bitumous and quite thin, so very easy to apply, though two or three coats are used. It inhibits rust, is quite cheap, and completely non-toxic (hence its name).
It didn't seem to foul too quickly, and is scrubbable (unlike gas-works tar, does anyone remember that?). But it was only ever used for craft on fresh water.