The tours to visit the cave are reasonably priced, you get to boat into it and around. The guide tells you about the rock formations and shows the most interesting ones. Our boat was half empty, compared to other ones at the same time which was nice.
It's like a little maze, it would've been a bit difficult without a guide as you have to crawl in some spots and there are extra corridors. It isn't huge enough to actually get lost but when you loose track and imagination starts to work it might be a bit stressful in a dark cave!
Again, guide is useful! This cave has a terrible history. The guide pointed us an arm bone stuck between the rocks from when someone was falling... there is a collection of broken skulls in the grotto too.