While in Tonga we visited the Swallows Cave, off Va'vau. The trip was amazing. Inside the cave, the water was so clear that we could see the bottom of the ocean 50 metres below. Fish swam, and so did we. Above us, the swallows nested in their mud nests, precariously clinging to the ceiling of the cave.
The cave itself seems to be somewhere that people, both local and tourists, write their names in the rock. Generally people seemed annoyed by it, but given that locals have been heading out, and climbing as high as they can in the cave to write their name, or the name of a loved one on the wall, it was hard not to see something so simple and delightful in it. Something like a local flavour of carving initials in a tree.