The southern coastal sea of Korea is shallow (<50 m) with very complex coastal lines and hundreds of islands. The coastal water is connected with Korea Strait (>100m) in the south and the narrow Jeju Strait (>100 m) in the west. Along the coast there are many ports and harbors that are located mainly in the landward side of the embayments. Among 5-6 typhoons passing near the Korea Peninsula in a year, 1 or 2 typhoons are used to be disastrous to the people and properties in the low land. However the dynamic response of coastal waters of this area to the harsh conditions is far from clear understanding. We use the numerical model, the ROMS, to analyze the dynamic response of semi-enclosed bays in the southern coast of Korea to the typhoon forcing. The forcing is coupled with time- and space- varying parameters such as typhoon winds, pressure, waves, tides and buoyant effect due to fresh water from land. The dynamic responses are analyzed in terms of 3 dimensional flow structure and sea surface variation adopting high resolving dry/wet scheme according to the different set of forcing parameters.