You can choose between a number of options - guided walk, rafting or tubing. I took the middle option of black water rafting. And reccommend it.
After being outfitted with miner's helmuts we all piled into the raft. The guide asked us to turn our lights off and we drifted along in the pitch black and the silence. We reached the main glow worm cavern and it was quite incredible. Definately worth seeing.
The guide was maybe a bit too enthusiastic as he told us all about the life style of what are basically maggots hanging above our heads. Tune him out, enjoy the view and try not to shriek if one of the maggots happens to fall on your head.