An erodible antifouling coating composition for application, for example, to ship's hulls to potentially prevent the adhesion and build-up of fouling agents on the hull is described. The coating composition includes 10 to 60% by solids weight of an erodible binder system that excludes a triorgano tin based binder; one or more antifouling agents; and 1 to 10% solids weight of a mixture of silicone oils, wherein the mixture includes a first and second silicone oil each comprising alkyl and aryl groups attached to silicone in a different ratio. A process for producing the composition, a substrate coated with the composition, and a process of coating a substrate with the composition are also described.