Because there’s just one main tide a day in the inner Gulf, the reefs of the Ko Chang archipelago are much less colourful and varied than Andaman coast dive sites, and they can get very crowded, but they’re rewarding enough to make a day-trip worthwhile. The main dive and snorkel sites are west of Ko Mak, in the national marine park around Ko Rang and its satellite islets. These range from beginners’ reefs with lots of hard corals and anemones at depths of 4–6m, frequented by plenty of reef fish – including a resident ten-thousand-strong shoal of yellow fusiliers – and the occasional moray eel, to the more challenging 25m dive at the Pinnacles. There are also some technical wreck dives of Japanese boats from World War II and even some centuries-old Chinese trading ships. The coral around Ko Yuak, off Ko Chang’s Hat Kai Bae, is mostly dead, though some operators still sell trips there.
From about November to May, several companies run dedicated snorkelling trips to reefs and islands around Ko Chang, Ko Wai and Ko Rang. Tickets are sold by tour agents on every beach and prices range from B600 to B1500, depending on the size of the boat (some take as many as a hundred people in high season) and the number of islands visited. In general the more islands “featured” (sailed past), the less time there is for snorkelling, though nearly all the actual snorkelling happens around Ko Rang.