This beautiful 70-sq-km marine national park is known to divers the world over. Lying 70km offshore from Phang-Nga Province, it has smooth granite islands that are as impressive above the bright-aqua water as they are below, topped with rainforest, edged with blindingly white beaches and fringed by coral reefs. Coral bleaching has killed off many of the hard corals, but soft corals are still intact, the fauna and fish are still there and it remains a lovely (and popular) place to dive.
In 1998 the park was expanded from its original nine islands to include Ko Bon and Ko Tachai; both have remained unscathed by coral bleaching, making them some of the better diving and snorkelling areas. Two of the 11 islands, Ko Miang and Ko Similan have ranger stations; the park visitors centre and most activity centres are on Ko Miang. ‘Similan’ comes from the Malay word sembilan, meaning ‘nine’, and, while each island is named, they’re more commonly known by their numbers.
Hat Khao Lak, where most dive schools are based, is the park's jumping-off point. The pier and the mainland national park headquarters are at Thap Lamu, 12km south. There's a visitors centre on Ko Miang.
Sadly, the onslaught of mass tourism means that many Similan beaches and dive/snorkel sites get completely packed with day trippers. There can be huge queues to climb up viewpoints and some snorkelling outfits go so far as to feed the fish, which is a big ecological no-no. That would never happen if this were a national park! Oh, wait…
Promisingly, however, overnight stays were banned on the Similans in 2018 (though divers can stay the night on a liveaboard) and Ko Tachai is now periodically closed to day trippers as part of an annual environmental review. A new quota system restricts the number of visitors that can visit the islands – it's a good idea to book ahead during peak periods to ensure you can get on a boat.