That is a droplet colliding with the rebound column of the preceding droplet.
I have seen many beautiful pictures of Droplet Photography–like Rick’s. I know for sure it is NOT easy–at least not for me. I want a taller column to begin with. Then, it takes the right timing to get a collision and the forming of a crown by the second [follow] droplet. Camera position matters as well. Rick has very nice height and camera angle. Cheers to him!!!