Abstract: A method of producing an algae growth-repellent underwater coating and the resultant product is to be such that it can be operated and performed without causing environmental pollution.For that purpose, there is added to an underwater paint or the like, a zinc-bearing additive comprising (CN).sub.6 -complex salts of hydrocyanic acid, in particular hexacyano iron(II) acid or hexacyano iron(III) acid. Zinc ferrocyanide and/or zinc ferricyanide is/are added to a colorless underwater paint, as a sole or additional pigment, in particular mixed with potassium ferrocyanide or ferricyanide or yellow soda or yellow calcium.