Waterfalls & hotsprings in north Bali
Bali is a volcanic island that has 4 big mountain lakes. Put that together and you have waterfalls and hotsprings. Of course the Balinese are wise to what tourists want, and quickly set up some sort of food and drink stall, or even a ticket booth.
There are at least 4 big waterfalls in north Bali, probably more. These are Git Git, Sing Sing, Blahmantung and Yeh Mempeh. Close to the Buddhist monastery you will find hot springs at Air Panas Banjar. Heading east along the main to to Singaraja is a place called Air Sanih, its freshwater springs a great place for a cooling dip.
Other than that, I can say that Bali has plentiful rivers and streams and there is nothing like stopping the car, hiking down the bank and taking a refreshing dip just like the locals do.