Marine environmental monitoring is critically important to detect environmental hazards at an early stage and to take the appropriate actions. However, monitoring, as has often been the case in the past was centered on the observation of the result, is very much like when humans consult a doctor after feeling sick to diagnose the ailment. From here on, we should consider turning to the idea of "preventive care", adopting necessary measures before any clear symptoms are apparent. This article outlines a new monitoring and valuation technique labeled as the "Health Examination" for the sea.