Once this island was a remote backpackers paradise accessible only from the mainland if you could persuade a local boat to take you there.
Now since the concept of swimming through a cave to access a stunning beach was popularised in the movie The Beach the island the back packers called pearl Island is an attraction that brings packed day boats to the anchorage in droves.
We anchored Ocean Emerald off Tham Morakot, or Emerald Cave, as tourists know it.
Here you can swim a short distance, at high tide, through a water-filled cavern part of which lies in virtual darkness to reach a hong.
A hong is a cave otherwise shut off from the outside world. In this case the hong with its beautiful sandy beach is open to skies because the top of the dome has collapsed to allow sunlight to flood into the space. It is a very magical space that if you were there before the day trippers arrived would be truly magical.
As it was we were enthralled with the way that tens of people wearing lifejackets and clearly somewhat afraid of the water were towed through the cave in single file each person clinging onto the life jacket of the person in front of them for dear life.