Really great work on the gestures! I had considered using various hand shapes to denote different effects, but decided not to because I thought it would be too complicated to make. You nailed it!
I did have some issues at first (making the "okay" symbol) due to the controller mapping. After reading the comments and creating a custom controller mapping I got it working tho and finger shooting water balls is a lot of fun!
I've had the same issues on most of the Unity games using SteamVR controller mapping. Is it an issue with the same Unity VR template that has red glove hands that everyone has been using?
Edit: Forgot to add that I was really impressed with the spatialised audio as well. It's so important for feeling like you are in the space.