Very cool shots! I have been wanting to try some splash photos. I’ll need to watch a few tutorials as I have no idea how it’s done. Are you using ocf?
Whatever the right way is, I'm sure I didn't do it. I filled a pot full of water and submerged two lume cubes in it. I put a nifty fifty on the camera and stopped it down to f8 for a little more depth of field. I jacked the ISO up to 6400. The shutter speed ended up at 1/6400. I held the coin where it would enter the water, set focus, and then turned auto focus off. In electronic shutter mode, the camera will shoot 20 frames per second. Even at that it took a couple of sequences to get what I wanted.