Longfeng Waterfall (中文版: 龍鳳瀑布) is a small waterfall in Taoyuan, Fuxing District (桃園市復興區). It's only a five minute walk from the top of Xiaowulai Waterfall (小烏來瀑布). The first tier looks deep and would be great for swimming and diving (off the top) but I didn't test it due to how crowded it was. I was too self-conscious to be the only one swimming. I very much want to go back and test it on a less crowded day though.
There is another tier above the first one. It's very easy to get to. Just climb over the fence and walk back 50 meters to the base of the waterfall. It's very pretty, but not deep enough to swim in.
Taoyuan City, Fuxing District
Detailed Map: https://goo.gl/83U9sU