Eastward sites
Sites on the eastern side of the islands tend to be sand covered fringing reefs predominantly made up of hard coral. The reef plateau’s are around 5-10 metres deep and from here you have gentle slopes heading down to the reef edge at around 20-25m. The Eastern sides of the Similans also tend to have more gentle currents. This makes the Eastern dive sites ideal for both divers of all levels and snorkelers too. On Eastern sites you can expect to see a huge variety of coral reef fish. On sand passes look out for garden eels, blue-spot mask rays and the endemic blue-spot jaw fish. Specials include harlequin and robust ghost pipefish, short pouch pygmy pipehorses and hawksbill turtles.
Westward sites
Sites on the west side of the islands are a little different. Here giant granite boulders tumble to the sea bed easily reaching depths of 40m. The more exposed side of the Similans can be prone to stronger and more unpredictable currents. The currents have kept the boulders free from a build up of sand, leading to boulder dive sites with a variety of canyons, tunnels, swimthroughs, archways and caverns. It can be more challenging diving but hopefully the increased chance of larger pelagics makes up for that. Also keep an eye out for andaman sweetlips, dogtooth tuna and anglerfish.
Koh Haa
Possibly some of the most underrated diving in the whole of Thailand, Moo Koh Haa (literally ‘five island group’) sits almost halfway between Hin Daeng and Phi Phi and is part of the Ko Lanta National Marine Park. There are actually several dive sites around Ko Haa but the highlights are Ko Haa Lagoon, Ko Haa Neua, and Ko Haa Yai.
Around these amazing islands you can see pinnacles, walls, boulders, caverns, and swim-throughs. Ko Haa lagoon is ideal for night dives, courses, and snorkelling, while The Chimney and The Cathedral offer things that you cannot see on other Thailand liveaboard itineraries with caverns, swim-throughs and chambers littering the sites. Ko Haa has varied marine life too, with ornate ghost pipefish, morays eels, octopus, hawksbill turtles, sea horses, marble rays, and sometimes even leopard sharks.
Hin Daeng & Hin Muang Site
These two sites are pinnacles (translating directly as Red Rock and Purple Rock) in open ocean, reaching down to over 70m, and are best known for manta ray and whale shark encounters but, whether they are sighted or not, the sites also offer giant moray eels, pharaoh cuttlefish, schooling rainbow runners and snappers, barracudas, groupers, fusiliers and blue fin trevally. On the pinnacles, there are fields of Magnificent Anemones, walls of Hemprics soft corals, and huge gorgonian sea fans.
Almost perpetual good visibility and dramatic topography combined with huge fish number makes for excellent liveaboard diving.