I got some pieces of bamboo yesterday and remembered seeing once a "japanese bamboo water thing", turns out it's called a Shishi Odoshi. They are used to scare away animals that might be feasting off your crops. Relatively simple to make but the balance of the tipping piece in the center is quite critical. It also depends probably how hard it rains (I'm assuming it wil work when it rains, but you could just feed the thing with a pump in a pond) how well this will work. Tomorrow we should get some rain so Im curious to see if it works then. In the meantime watch a video of the Shishi Odoshi in action.