The Naga Cave is about 3 to 5000 years old. The Naga Cave is located in Phang Nga Bay Thailand about half an hour from 1 of the main tourist piers. The Naga Cave is hard to reach: the way to the Naga Cave depends on the tide. With low tide you cannot reach it because the waterways in the mangroves are dried up. The best times to go is during high tide and incoming tide and gives you longer time in the cave.
The Naga Cave is about 20m high and decorated with stunning limestone stalactites and stalagmites. The moist level is quite high giving the limestone that greenish colour.
The Naga Cave used to be an ancient burial ground. You can find some ancient wall paintings as well.
If you up for it, you can climb up at the the back of the cave. When you reached the top you have a stunning view over Phang Nga Bay. Only recommended for active people.
Click to enlarge. The photos are not my best quality but it will give you a nice impression of what you can see.
Wear shoes with lots of grip, bring a headlight, bring tons of mosquito spray because its mosquito infested. For photographers: bring the widest angle lens you have (FF 14-24mm or 16-35mm, on APS-C a equivalent of that for example 10-20m, or a prime: the Rokinon/Samyang 10mm is actually a perfect lens) a tripod, a camera that is capable producing good images at high iso and some filters. As you see on the photos, the scenery is very contrasty so high dynamic range can be required. I never tried a fisheye lens here, but it should do fine and can create some nice effects as well. The 8mm Rokinon is something I had in mind myself.
The Naga Cave in Phang Nga Bay is open all year, but can only be reached during high tide. So plan your trip well. Most boat operators advise you not to go because entering the cave can be hard. Also because of the tide, they are afraid that they will get stuck. There is no stairs or anything that are normal for common tourists. This cave is more for people and photographers looking for some adventure and stunning nature/landscape.