Thanks very much! When I fly over water I generally use a polarizer filter that is combined with a neutral density filter or a ND/PL as it's known. You can get polarizers by themselves but I usually need the ND filter as well so go with the combo glass. Polar Pro is the brand I use but there are others out there. Before flight, the PL can be turned to adjust how much effect you want it to have from none to full. Besides cutting down reflections a polarizer will also add some color saturation as well.
Almost all my YT videos are manually flown but I do also use waypoints from time to time. Btw, here's a video that you may find helpful in regards to filters: