There are some major problems with this device in practical application. Even if it charges beautifully, how do you expect to properly deploy it in a stream or river? You think you can tie a rope to it and just toss it in?
You are going to need to mount it rigidly to a pole or other hardware that will keep the base stationary while the propeller rotates, and somehow keep it stabilized over the river, from the side or if there is a bridge. If you just throwing it in the entire device will probably spin until your rope gets twisted up, and will bounce around in all directions. We don't know if this floats or sinks, and either way it will be a mess without some support or someone holding the base rigidly and at the proper depth to allow all rotation torque on propeller only.
Conclusion: As is, without additional hardware for proper deployment, it is a FAIL.