offer poor anchor points. Coatings Non-toxic coatings Non-toxic anti-sticking coatings prevent attachment of microorganisms thus negating the use of biocides. These coatings are usually based on organic polymers. There are two classes of non-toxic anti-fouling coatings. The most common class relies on low friction and low surface energies. Low surface energies result in hydrophobic surfaces. These coatings create a smooth surface, which can prevent attachment of larger microorganisms. For example, fluoropolymers and silicone coatings are commonly used. These coatings are ecologically inert but have problems with mechanical strength and long-term stability. Specifically, after days biofilms (slime) can coat the surfaces, which buries the chemical activity and allows microorganisms to attach. The current standard for these coatings is polydimethylsiloxane, or PDMS, which consists of a non-polar backbone made of repeating units of silicon and oxygen atoms. The non-polarity of PDMS allows for biomolecules to readily adsorb to its surface in order to lower interfacial energy. However, PDMS also has a low modulus of elasticity that allows for the release of fouling organisms at speeds of greater than 20 knots. The dependence of effectiveness on vessel speed prevents use of PDMS on slow-moving ships or those that spend significant amounts of time in port. The second class of non-toxic antifouling coatings are hydrophilic coatings. They rely on high amounts of hydration in order to increase the energetic penalty of removing water for proteins and microorganisms to attach. The most common examples of these coatings are based on highly hydrated zwitterions, such as glycine betaine and sulfobetaine. These coatings are also low-friction, but are considered by some to be superior to hydrophobic surfaces because they prevent bacteria attachment, preventing biofilm formation. These coatings are not yet commercially available and are being designed as part of a larger effort by the Office of Naval Research to develop environmentally safe biomimetic ship coatings. Biocides Biocides are chemical substances that kill or deter microorganisms responsible for biofouling. The biocide is typically applied as a paint, i.e. through physical adsorption. The biocides prevent the formation of biofilms. Other biocides are toxic to larger organisms in biofouling, such as algae. Formerly, the so-called tributyltin (TBT) compounds were used as biocides (and thus anti-fouling agents). TBTs are toxic to both microorganisms and larger aquatic organisms. The international maritime community has phased out the use of organotin-based coatings. Replacing organotin compounds is dichlorooctylisothiazolinone. This compound, however, also suffers from broad