For lakes and reservoirs an overall assessment is given to each water body. A five plus one grade system applies to the freshwater system and a four plus one system to coastal areas, with a lower grade indicating lower levels of pollution. For marine areas a separate four plus one grading system is used to assess water quality with grade I the most pristine, grade IV the most polluted and water meeting grade II standard deemed appropriate for bathing. Coastal water quality along the three main seas monitored varies considerably.