This morning, when I was making that second video, I first thought that the phenomenon could only occur in the morning or evening, when the sun angle is low. (I know that it can't happen at the dock, because things are much too crowded for the sun to reach the water to reflect inside.)
But isn't it true that if the water is moving, there will almost always be a surface that is correctly oriented to reflect light onto the overhead? I think it must be so. So it should be possible to see the moving patterns at any time of day if there is sun, the boat is oriented more or less broadside to it, and the water is gently moving.