Euphotic zone depth, z 1%, reflects the depth where photosynthetic available radiation (PAR) is 1% of its surface value. The value of z 1% is a measure of water clarity, which is an important parameter regarding ecosystems. Based on the Case-1 water assumption, z 1% can be estimated empirically from the remotely derived concentration of chlorophyll-a (), commonly retrieved by employing band ratios of remote sensing reflectance (R rs). Recently, a model based on water's inherent optical properties (IOPs) has been developed to describe the vertical attenuation of visible solar radiation. Since IOPs can be near-analytically calculated from R rs, so too can z 1%. In this study, for measurements made over three different regions and at different seasons (z 1% were in a range of 4.3--82.0 m with ranging from 0.07 to 49.4 mg/m3), z 1% calculated from R rs was compared with z 1% from in situ measured PAR profiles. It is found that the z 1% values calculated via R rs-derived IOPs are, on average, within ~14% of the measured values, and similar results were obtained for depths of 10% and 50% of surface PAR. In comparison, however, the error was ~33% when z 1% is calculated via R rs-derived . Further, the importance of deriving euphotic zone depth from satellite ocean-color remote sensing is discussed.