We are flying surveys over the ocean using a fixed-wing UAV with Sony RX1RII camera pointed at nadir. We want to minimize sun glint and sky reflection in our imaging. Following NASA guidelines we often (not always) fly survey lines directly toward or away from the Sun, and we generally fly when solar elevation is between 30 and 45 degrees above the horizon. Even with these constraints our images often show significant sky reflection, regardless of whether clouds are present or not. The camera does have a circular polarizing filter, but it's not clear how to set the filter angle before the flight. Skylight and glint doesn't seem to depend on just solar geometry - waves, swell and ripples can contribute too. How best to adjust the polarizer filter for these factors ahead of time? Difficult because we don't have the same overhead scene of the sea surface that the UAV has during flight. Any recommendations are welcome!