We present the up-to-date the operational coastal ocean observing system (COOS) in Korea, including a network of wave buoys, wind stations and buoys, tide gauges, high-frequency radars, and bi-monthly hydrographic conductivitytemperature-depth surveys. The operational COOS is designed to monitor the regional circulation and physical and biological processes around the Korean Peninsula, characterized by tide-dominant currents in the Yellow Sea (YS), geostrophic currents and regional boundary currents in the East/Japan Sea (EJS), and complex coastal currents associated with these two distinct regional currents in the South Sea of Korea (SS).