Lu had two ideas. The first was to use Watershot to continuously drain the water from his surroundings before the rain could hit him. The other was to use Watershot to dry himself.
It was just that Watershot didn't need rain. It created bullets of water from the moisture in the air.
When the rain started falling, there was too much water in the air for Watershot to be as effective as Lu had hoped. But it was just a matter of experience, at least in Lu's eyes. If he was better at using Watershot to its full potential, he could tweak it so that it took as much water as he wanted it to.
So, while waiting for the storm to pass, Lu practiced like crazy and spent all of his mighty world essence trying to cast Watershot. He ended up creating a pond around him as he gathered more and more water by creating large spheres of water and then dropping them.
