Lying flat in my kayak to float under the rock wall just inches above my nose, I couldn’t help wondering how long until the tide would rise, trapping my fellow kayakers and me on the far side of the bat-filled cave we had just paddled through. But after emerging into the secluded, pristine lagoon, with sheer limestone cliffs rising up to the blue sky above, and a family of macaque monkeys descending from the trees, I was in no hurry to leave.