My cat has decided to start dumping his water bowl over. Any ideas on how to get him to stop?

We have one of those self waterers. So it’s like a rectangle tray with a plastic bottle full of water on the top. My youngest cat, Timmy, is about 10 months old. He all of a sudden has decided it’s really fun to put his paw in the tray and pull really hard, spilling water all over the place. The first couple times he did it, I changed the water, thinking maybe something had fallen in it and it was dirty. I realized that wasn’t the problem, because he continues to do it. I tried putting the self waterer up and putting a different bowl of water down, but he did it to the regular bowl of water also. Has anyone else had this problem? Do you have any suggestions of what I can do to get him to stop?