There is always the tale of the boating Doctor who decided to mix in a vial of anti-biotic into his bottom paint! Makes sense since we are dealing with organic matter and an anti-biotic in sufficient strength and quantity just might repel the critters. I believe this evolved into marine biocides.
Anti-biotics, pepper flakes, pine pitch or cat urine mixed into a gallon of paint on a full moon; whatever is your passion and whatever you think works.........enjoy yourself!
Bob