This is a nice day trip to do and a must see at least once when in Palawan.
It is part of the world's New Seven Wonders of Nature and you can understand why once you go. The underground river is truly beautiful and impressive.
I also enjoyed the fact that they provide an audio system so you can learn more about this place while on the boat cruising underground. And the park works hard to keep this place clean and green which is great to see.