PEMSEA, which began as a regional mechanism as part of a regional project of the Global Environment Facility (GEF) in 1994, utilizes the framework of integrated coastal management (ICM) to work on sustainable development with aims to achieve harmony between the development of coastal areas and the ocean and environmental conservation in East and South East Asia. As of February 2013, 11 countries in East and South East Asia (Japan, Cambodia, China, North Korea, Indonesia, Laos, the Philippines, South Korea, Singapore, East Timor and Vietnam) have joined as partners and 20 non-governmental organizations are also affiliated. While PEMSEA's activities do not have any legally binding power in accordance with any conventions, etc., its basic principle is "partnership" for the purpose of sharing goals and strategies, and steadily completing what they are able to do.
Consent and ratification by eight countries of PEMSEA (Cambodia, China, North Korea, Indonesia, Laos, the Philippines, South Korea and East Timor) led to PEMSEA receiving the qualification of an international legal personality in November 2011. Therefore, this development is indicative of PEMSEA's evolvement from a regional project of GEF into an international organization.
PEMSEA conducts ICM with local governments acting as the main body. As of February 2014, its initiatives take place in 33 locations in 11 countries. In September 2013, Shima City joined PNLG (PEMSEA Network of Local Government) as the first Japanese local government.
OPRI is a non-governmental partner of PEMSEA and Hiroshi Terashima, President of OPRI, has made contributions to PEMSEA's development for many years as the former chairperson of the technical session. Presently, Mr. Terashima still actively takes part in PEMSEA activities, including attending partnership council meetings, participating in various working groups, holding a workshop at the East Asian Seas Congress, and supporting PNLG, among others.