The Contraption (Owen+Lee)

Owen sat at the bank of the Zephyros Creek, with three baskets full of not-blown-up balloons, straight from the camp store. What? They were having a sell! He took each one, dipped it in the water, then tied it up and carefully put it to the side. This was a water balloon prank; he was going to build some sort of cannon and release the water balloons, and watch the demigods scatter. It'd be a fun prank. But, Owen wasn't cruel; so he also bought twenty towels, in which he'd launch with the balloon. Towels could be launched, right? Well, not scientifically, but he'd find a way.

He, when he was done with the balloons, got a huge log. He'd place in the middle of two already-there boulders, then attach a bowl to one side of the log, the elevated side. He'd then find a way from there to launch it, by putting the balloons in the bowl. But, first thing first, he needed to get the log over there. Unluckily, he was doing this prank solo, and he wasn't strong enough to lift it, and he didn't have any powers that helped him with his strength. These were the times he was a bit jealous about the Ares kids.

"Help, anyone? I gotz to unleash the balloon-y wrath!"