Koh Haa is a diverse marine site near Koh Lanta, Thailand, featuring a complex topography of reefs, walls, caverns, and drop-offs. Divers and snorkellers can explore depths ranging from 1 to 45 metres, with an average depth of 15 metres. Access is strictly by boat, as the site is located 20 kilometres from shore. Conditions generally feature mild currents and visibility between 15 and 30 metres. A thermocline may occur at greater depths, leading to temperature drops and reduced visibility. Hazards include boat traffic, overhead environments within the caverns, and sharp coral. Species recorded around this area include wrasses, Titan Triggerfish, Giant Moray, and Indian Lionfish.

The Cathedral at Hin Daeng and Hin Muang is a complex site featuring a pinnacle, wall, and cavern system. Divers navigate depths ranging from 7 to 36 metres, with an average depth of 20 metres. Access is strictly by boat, as the site is located 20 kilometres from shore. Conditions include mild currents, though surge and strong currents can occur. The visibility fluctuates significantly between 5 and 40 metres. Due to the overhead environment and depth, this site is suited for intermediate divers. Hazards include the deep nature of the site, potential overhead environments, surge, and strong currents.

Koh Haa #3 is a diverse site featuring a reef, wall, and cave system. The reef extends from shallow water to a depth of 30 metres, with an average depth of 15 metres. The site is accessible only by boat and is suited for intermediate divers due to the overhead environment within the cave. Visibility ranges from 5 to 30 metres, and mild currents are typical. Water temperatures generally remain between 28 and 31C, though thermoclines can cause localized drops in temperature and visibility. Divers should maintain careful buoyancy control to avoid contact with sharp coral and cave walls.

The Lagoon at Koh Bida Nok features a diverse underwater topography including a reef, wall, and drop-off, complemented by caverns, swim-throughs, and a pinnacle. This site is accessible by boat and is suitable for beginners, with depths ranging from 1 to 35 metres and an average depth of 10 metres. Divers encounter mild currents and visibility that varies between 5 and 40 metres. The site supports night diving and offers a 50-minute typical dive duration. Hazards to note include boat traffic, deep sections, overhead environments, strong currents, and potential encounters with jellyfish, lionfish, stonefish, and sharks, as well as sharp coral.

The Chimney at Koh Bida Nok is a diverse dive site featuring a complex topography of reefs, walls, caverns, and a pinnacle. Divers can explore a drop-off that ranges from 5 to 35 metres, with an average depth of 18 metres. The site is accessed by boat and is suited for intermediate divers due to the presence of overhead environments and moderate currents. Hazards include potential entanglement, sharp coral, and strong currents. Typical dives last approximately 50 minutes, with visibility ranging between 15 and 30 metres. Water temperatures remain warm throughout the year, typically between 28 and 31 degrees Celsius.

Koh Bida Nok is a marine site featuring a combination of reef, wall, and cave topography. Located 56 kilometres from shore, the site requires boat access. Divers and snorkellers can explore depths ranging from 5 to 30 metres, with an average depth of 15 metres. Conditions are generally characterised by mild currents and visibility between 10 and 25 metres. Water temperatures remain consistent throughout the year, typically between 29 and 31 degrees Celsius. The site is suited for intermediate-level divers. Hazards at this location include boat traffic, deep sections, overhead environments, and sharp coral. Guided tours and boat charters are available for those visiting the area.

Hin Daeng is a remote pinnacle and wall system located 70 kilometres from shore. The site features a dramatic drop-off with depths ranging from 5 to 60 metres, averaging 25 metres. Due to the exposed location, divers encounter strong currents and potential surf, making this an advanced dive site. Visibility varies between 10 and 30 metres. Water temperatures typically range from 26C to 29C, though thermoclines can create cooler layers at greater depths. Access is strictly by boat, and dives typically last 60 minutes. Divers must be prepared for deep diving conditions, including the risks of decompression and nitrogen narcosis.

Ko Rok Nai, located near Koh Haa, offers a varied underwater environment featuring reef sections, a cave, and drift diving opportunities. Depths range from 5 to 20 metres, with an average of 12 metres, making it suitable for beginners. Visibility typically spans 10 to 30 metres. Water temperatures are warm, ranging between 29 and 31C. Divers should be aware of moderate currents and potential hazards including lionfish, sea urchins, and sharp coral. Boat traffic is active at the surface, requiring careful ascent procedures. Species recorded around this area include wrasses, Moorish idols, pufferfish, butterflyfish, anemonefish, and parrotfish. Night diving is available at this site.