good luck changing the batteries -_- :-D
nice work....but I see that the generator is 3.6V...so maybe try one 18650 battery between the light and generator...this way the generato charges the battery and the battery powers the light...then it will not be instant on or instant off and you can still see the bathroom when the light is off for a little while after. Also, try adding an on/off switch between the battery and light as well then you can switch it on and off when using the battery power generated from the water generator; which charges the battery. could become very efficient! Hope this gave you ideas on how to improve.