In addition to incurring civil liability under RCW 90.58.210, any person found to have wilfully engaged in activities on the shorelines of the state in violation of the provisions of this chapter or any of the master programs, rules, or regulations adopted pursuant thereto shall be guilty of a gross misdemeanor, and shall be punished by a fine of not less than twenty-five nor more than one thousand dollars or by imprisonment in the county jail for not more than ninety days, or by both such fine and imprisonment: PROVIDED, That the fine for the third and all subsequent violations in any five-year period shall be not less than five hundred nor more than ten thousand dollars: PROVIDED FURTHER, That fines for violations of RCW 90.58.550, or any rule adopted thereunder, shall be determined under RCW 90.58.560.