No Stupid Questions

As others have stated, this is indeed already something that exists.

I'm here to go on record to point out something that most people seem not to know about paintballs, which is that their "mess" is intentionally made of materials that are washable and readily water soluble, for obvious reasons. I've seen a lot of hyperventilating coming from certain individuals over the years about youths supposedly being able to permanently vandalize things at a distance with paintball guns and therefore they should all be banned. This is fiction. Rest assured that anything paintballs will do to your stuff can be cured by simply rinsing it down with your garden hose.

(This is obviously notwithstanding suitably motivated individuals from rolling their own ammo out of whatever-the-hell. A paintball gun will dutifully send downrange anything round and roughly .68" in diameter, with varying degrees of success depending on the density and/or fragility of the object in question.)

yes. It's a thing. https://mcsus.com/products/68-water-balls-tube-of-10 No clue if they're good or not, but they exist.

There's also paintballs with clear paint, or reballs which are basically just rubber balls meant to be fired out of a paintball gun.

Paintballs are trickier than just a water balloon. They have to be rigid/strong enough to survive the blast of co2 or compressed air that propels them, then they have to be soft enough to break on impact without harming the other player.

They also just aren't that messy. I worked under the table as a referee at a Paintball place when I was 13, and we played such that gameplay didn't stop when refs were doing paint checks. We'd toss people out if they were intentionally focusing on us but I got lit up probably 10+ times a day, every weekend for 2 years. My jersey and slider pants came clean in the wash every time, and to this day the only lasting blemishes are the shredded fabric on the knees/elbows/ass from when I dove and slid a lot.

There was a string of people swapping marbles into paintball guns for a few years here locally.

The paint in the paintball is already mostly just dyed water. It doesn't stain. But balloons they are not. The casing is much more rigid. I don't think putting an actual water balloon the size of a paintball would work too well, since it'll probably deform and possibly pop inside the barrel.

Well, I wouldn't call them balloons. They are still pretty hard, probably so they can survive being fired. So at least it wouldn't make the game more child safe.

If it's a round ball that's .68 caliber, sure. I mean it's a ball being launched.

However, are any waterballs even that size? And why? A waterball that was wet would probably jam up, so you'd end up shooting a dry one and it seems like a lot of effort to reinvent the wheel.

Couldn't see why not, only thing that might say no would be I expect water is less dense than paint so the weight would possibly be different if they where both full.

Freeze some water into suitably sized balls. I guess that technically fits the design spec.