Of course, you should water-proof the hubmotor, but....
This guy uses a bunch of spoons as his water-wheel cups. I found this when researching the best link to use as a reference for "Pelton" water turbines. Back in the gold rush, water wheels were used for anything they were useful for. In mountainous areas, there was high head, and attaching a small mill-pond to a stream with a steeply-angled pipe would create a water jet at the bottom (high head pressure, low volume).
The initial improvised versions had flat paddles attached to a common wagon wheel. It was fast and cheap, but...increasing the efficiency would lead to making the paddles cup-shaped, to capture some of the turbulent energy that was flowing off to the sides with the flat-paddle versions.
The way that the story goes is that...a mining worker named "Pelton" was repairing on a water-jet wheel with cupped paddles, and the wheel slipped off a little to the side. This made the jet hit the rounded cup near the edge instead of the center, and then exit at the other edge, after dissipating its energy by flowing across the curved face and exiting 180-degrees from it's entrance. He noticed that the wheel spun faster and seemed to have more torque.
At some point, he considered that the sideways force on the wheel was wasted energy, so he devised a dual "split cup", where the water jet shot at the center, and the stream was split with half flowing to the left, and the other half flowing to the right.
A short while later, a carefully considered study revealed that as the wheel spun, the jet of water did not enter the next split-cup at the optimum angle, and so a top-center cut-out was included, with experiments verifying the improved performance. The most advanced form of the design was called the "Pelton Doble". If you are improvising Pelton cups from half-moon sections of PVC pipe, you might simply alternate the flow, so one cup flows to the right, and the next flows to the left.