A B S T R A C TWe introduce technological achievements while developing real-time ocean monitoring buoy systems in the key coastal regions around the Korean peninsula, and highlight their potential contribution to oceanographic studies in the region. Major achievements are an integration of physical and biogeochemical sensors, real-time and two-way communication, sustainable maintenance with stable power supply and mooring design, and the two-way control of sensor and sampling strategies with high sampling rates (as often as every minute). The time-series data from two buoy systems deployed in the key coastal regions are given as examples to show their potential use in studying oceanographic issues, such as major current variations along the east coast of Korea, wind-driven episodic events including typhoon passages, and frequent changes due to internal wave passages. The real-time and high-frequency monitoring of biogeochemical properties of seawater together with physical parameters could be used for numerous oceanographic studies in the coastal region, i.e., air-sea gas exchange, harmful dinoflagellate bloom, interaction between physical and biogeochemical processes.