After prohibition of use of organic tin compounds, new antifouling agents have been used as substitute paints. In 2009, this lab re-conducted the same research from 2006 that focused on concentrations of chlorothalonil, dichlofluanid, and Irgarol in the major bays of Korea, in order to assess changes in concentrations. Among the new antifouling agents detected in 2006, chlorothalonil, dichlofluanid, and Irgarol 1051 were detected up to 4.19, 61.69, and 23.80 ng/L, respectively. However, in 2009, up to 67.96, 74.79, and 67.64 ng/L were detected. Compared to 2006, there were apparent increases in the concentration of all three compounds in all areas where the research was conducted. These results indicate the need for further research regarding the hazards of these compounds.