Incorporating an above-water 400m-long zip line, followed by a swim into the cave and then exploration of a pitch-black passageway of oozing mud, it's little wonder Hang Toi is the cave experience you've probably already heard about from other travellers. Upon exiting the cave, a leisurely kayak paddle heads to a jetty where there are more into-the-water zip-line thrills to be had. Don't take any valuables into the cave.
The Dark Cave can be visited independently or on tours booked with local accommodation.