The wetted surface area of recreational craft is often treated with special paint that prevents growth of algae and other organisms. The active substances in this paint (antifouling) are also emitted into the water. The extent of this emission is among others determined by the treated surface area.
The RIVM has developed a method to calculate the wetted surface area of recreational craft based on boat length. This is essential to assess the environmental effects associated with these emissions. The final result of this study is a weighted average value for the wetted surface area of recreational craft in Dutch marinas, including separate values for salt water, transitional waters, and fresh surface water.
Paints sold with this purpose are known as biocides. The safety of biocides for both humans and the environment is assessed during the authorisation phase of biocidal products. The active substance in antifouling paint may also be toxic to organisms other than those on the ship's hull.