Surin Islands

Three kinds of trip land here. Liveaboards out of the Khao Lak coast fold Surin into their Similan and pinnacle itineraries, working the islands through the settled part of the day and moving on overnight. The second is a speedboat run from the mainland pier, which makes the crossing most of the day's effort and leaves room for a couple of dives before the return. The third never gets on scuba at all: park tents and bungalows on the beach, and snorkelling straight off the sand.

The diving is horizontal rather than vertical. There are no walls; the islands are ringed by granite shelves that slope away gently, and you spend the dive swimming over the top of the coral rather than alongside it. What current there is collects in the channels between the islands, so those get run as drifts and timed to the tide while the rest of the park stays close to slack. Bottom times run long because the interest sits shallow, well inside no-decompression limits.

Warm-water years have hurt these reefs, and the park has closed individual sites before to let bleached coral recover, so guides swap the plan without much notice. What holds up is the format: bright, shallow, wide-angle reef that reads about as well through a snorkeller's mask as it does on scuba. That makes it a good fit for mixed groups where not everyone is certified, and for anyone happier spending an hour above living coral than staring into blue water.