Rotate based perpendicular to curve

I have been working on this script to simulate floating units at different water levels. I have them going straight up from a point from an irregular surface to water level at high tide (MHHW) and drifting to a point at low tide (MLLW). I would like to modify this script so that the units drift to spread out in different directions. I think I may need to rotate the circles that determine the center point of the second units to be perpendicular to the cull line. But I can't get it to work. Please help. note that I would like to keep the length of the line from the base to the floating object the same to simulate a tethered line at different water levels. Thanks to anyone willing to help!!!!