I have one video of beneath the water and one video of above the water. I plan to animate a mask where the waves hit the lens to combine the videos combine into one. I want to add a distortion effect for that curvy line where the waves are touching the lens, but have no idea where to begin.
Use a track matte where top half is white and bottom half is black to mask off one layer. Add a wave warp or turbulent displacement or some such animated distortion effect to the track matte layer to make it look like a wavy surface.