Worry about a dog having too much fun seems silly. He's just being a dog and staying cool in the water. It's a harmless way for him to burn off energy.
Seriously, some people act like dogs need a fun coordinator. Next they'll be trying to regulate how deep the water bowl can be or limit zoomies to approved hours. I mean, let the dude splash. It's not like he's planning a pool party with a suspicious guest list. We're really overthinking a wet dog living his best life.