Waterborne preservatives are aqueous solutions of salts that are toxic to the target organism. Mercuric chloride, patented in 1832, was the first of this type of preservative to be used. Today's waterborne systems are diverse and have been classified by Eaton & Hale (1993) as follows.

• Zinc-based compounds
• Copper-salt systems
• Fluor-chromate arsenate phenol (FCAP) mixtures
• Alkyl ammonium compounds (AAC)
• Boron compounds