The international specialist underwater hull organisation Hydrex Group recently published a White Paper called the Slime Factor. It points out that harmful growth of an invisible slime, coats any untreated, immersed surface within days if not weeks causing friction to increase with a commensurate decrease in speed. The effect of biological growth on submerged objects and has marked effect on ship performance. As the costs of fuel increases the escalation in fuel consumption becomes more and more significant to any ship operator, be it commercial or military. There are several approaches to living with this problem as a permanent solution has eluded man so far! Four different methods are discussed with the conclusion that a hard coating with regular underwater cleaning is the most effective cost saving solution in the long run as well as being neutral to the environment. [More]