Boulder City

Boulder City is a fully submerged Similan dive site of hundreds of massive granite boulders arranged in ridges and pinnacles across a sandy bottom, with three main clusters separated by sand channels that create the impression of an underwater city. The granite surfaces host soft corals and sea fans, and the formations attract abundant marine life including large schools of fusiliers and trevallies, predators such as giant barracudas and dogtooth tuna, reef sharks, rays (including manta and occasional whale shark sightings), sea turtles and a variety of reef species. The site lies about 1 km off the east tip of Similan Island 3 and must be reached by boat; divers commonly descend on a mooring line near the deeper boulders and drift along the formations. Depths range from rock tops around 12 m to about 35-40 m with a typical start on the sandy bottom at 30-35 m; currents are moderate to strong, visibility is often 20-30 m in clear conditions and water temperatures are about 27-29 °C during the November-April season. Because of the depth and currents the site is recommended for experienced divers and is often done as the first dive of the day.