Ko Ha (Five Island)

This guide to Koh Haa, six limestone islands inside Mu Ko Lanta National Park, opens with a mooring rope tied to a concrete block on the seabed and the reef that survives because every boat clips onto one instead of dropping anchor. It follows the park fees that fund the rangers and buoys, and traces the site's signature dive, a narrow rock chimney passageway where bronze cave sweepers hang in the current. Look for that same rope from the boat before you go in, it marks the line between a reef that gets sold and one that survives being sold.