This is an easy one to turn around!
I agree that it's just too intriguing for that age and that "popping" on the hand is ultimately counter-productive. Much MUCH better to catch him and redirect him to his own water activity. But, unless you can move it to an area where he can't see it or reach it (easier to do that for cats than dogs), accept that sometimes he will get to it before you notice, so keep a stack of dish towels nearby and show him how you use the towel to clean up and put it in the laundry room. Encourage him (SWEETLY, not chastising) to help. And keep less water in the bowls so there's less of a mess.
If you see your son going for it, redirect him towards his *own* water games. Toddlers are fascinated, even entranced by water, and running their hands under the faucet or pouring from cup to cup is a very soothing activity for them. Find a way he can play with it that won't make too mcuh mess. Give him a couple of cups with a little bit of water in them and let him pour them back and forth. (You may have to steady him if he's doing this over the sink.) Get a low children's table, and put a tray on it and allow him to pour water between cups over the tray. Or put slightly soapy water in a bowl, give him a small sponge, and let him scrub his plastic dinosaurs. I've seen a group of 10 toddlers gathered around a table happily cleaning toys for 20 minutes.
Having a waterproof smock is good, too.
I had one of those "Learning Towers" in the kitchen so he could stand on that and play with water in the kitchen sink, pouring water in between 2 plastic cups. He LOVED it.
Montessori schools encourage children to do all kinds of experimenting with water - they even have very low sinks so even the smallest kids can walk right up and work the faucets themselves. And they show the toddlers how to use a turkey baster to move colored water from one bowl to another, and they gradually make the droppers smaller and smaller until the kids can do it using a little eye dropper. (Gradually going from gross motor skills to find motor skills.)