The objective of this project was to develop sobriety tests that can be administered in the seated position to assist water patrol officers in detecting alcohol-related impairment in boaters. Four seated sobriety tests were administered to 330 boaters to determine the tests’ usefulness in classifying boaters as having blood alcohol concentrations (BACs) below the illegal limit (BAC<.08%) or above the illegal limit (BAC≥.08%). Data were obtained by a team of four marine officers and two civilian observers on Lake of the Ozarks in central Missouri. The overall correct percentages, sensitivity, and specificity of the tests were consistent with what is typically reported in literature on the roadside sobriety tests. The tests’ reliability was also consistent with what is typically reported in literature on the roadside sobriety tests. Thus, the four tests may assist marine officers with assessments of alcohol-related impairment in boaters.