Koh Nang Yuan offers a diverse underwater environment featuring coral reefs, submerged pinnacles, shipwrecks, and artificial reef structures. The site is suitable for all skill levels, with depths ranging from 4 to 40 metres and an average depth of 15 metres. Divers and snorkellers can access the area via shore or boat. Conditions vary, with visibility between 5 and 30 metres and mild currents. Facilities available include air fills, equipment rental, guided tours, parking, toilets, showers, changing rooms, and a cafe. Night diving is permitted. Hazards include boat traffic, deep sections, jellyfish, low visibility, nitrogen narcosis, sea urchins, sharp coral, and strong currents.

Mao Bay at Koh Nang Yuan features a combination of natural reef and artificial reef structures. This site is suitable for beginners, with depths ranging from 1 to 20 metres and an average depth of 10 metres. Divers experience mild currents and visibility between 8 and 20 metres. Marine life recorded here includes wrasses, porcupinefish, Titan triggerfish, and Bluespotted Fantail rays. Other species present are Pink Skunk anemonefish, Longfin bannerfish, and Blacktip grouper. Divers should be cautious of sharp edges on both the natural coral and artificial structures. Access is by boat, and dives typically last 45 minutes.

Hin Wong Bay is a large, horseshoe-shaped bay located on the north-east coast of Koh Tao. This site features a diverse topography including reefs, caves, pinnacles, drop-offs, and artificial structures. Depths range from 2 to 40 metres, with an average of 18 metres. Divers and snorkellers can encounter species such as Blue-barred Parrotfish, wrasses, Rabbitfish, and hard corals. Less frequently, visitors may spot Harlequin Sweetlips, Titan Triggerfish, Golden Butterflyfish, Longfin Bannerfish, and Magnificent Giant Anemone. Conditions vary with visibility between 2 and 25 metres and mild currents. Thermoclines may occur, and hazards include boat traffic and sharp coral. Access is available via both shore and boat, with facilities including equipment rental and guided tours.

HTMS Hanhak Sattru is a decommissioned naval vessel resting at depths between 13 and 24 metres near Koh Nang Yuan. As an artificial reef, the wreck features a complex superstructure that requires steady buoyancy control due to moderate currents. Visibility typically ranges from 14 to 30 metres, allowing for clear views of the vessel. The site includes enclosed sections that present an overhead environment, necessitating caution and the use of a dive torch for those entering the hull. This site is suitable for intermediate divers, with boat access required for all visits. Night diving is available, offering opportunities to observe nocturnal activity within the structure.

Hin Wong Pinnacle is a reef and pinnacle site located near Koh Nang Yuan. The site offers depths ranging from 5 to 30 metres, with an average depth of 15 metres, making it suitable for beginners. Access is by boat only. Visibility is variable, ranging from 5 to 30 metres, and currents are generally mild but can strengthen. Water temperatures remain warm throughout the year, typically between 28 and 31 degrees Celsius. The site features a complex structure of rock and coral, which is also available for night diving. Divers should be aware of potential hazards including jellyfish, sharp coral, and fluctuating visibility.

Tanote Bay, located on the east side of Koh Tao, offers a large reef area stretching along the coastline. The site features a mix of reef, artificial structures, and a sunken catamaran wreck located southeast of the prominent surface rocks. Depths range from 5m to 18m, with an average of 12m. Divers and snorkellers can encounter wrasses, blue-barred parrotfish, groupers, and porcupinefish. Other species include harlequin sweetlips, titan triggerfish, and the magnificent giant anemone. The site is suitable for beginners, though users should remain aware of boat traffic, surf, and sharp coral. Visibility varies significantly from 2m to 30m, and mild currents are typical.

Laem Thian is a cape located on the east coast of Koh Nang Yuan, Thailand. This site features a diverse underwater topography consisting of reefs, walls, caverns, and swim-throughs suitable for intermediate divers and snorkellers. Depths range from 3 to 35 metres, with an average of 15 metres. Divers may encounter species including wrasses, blue-barred parrotfish, porcupinefish, pink skunk anemonefish, golden butterflyfish, longfin bannerfish, moon wrasse, scissortail sergeant, rabbitfish, and bluespotted fantail ray. Hard corals, cabbage corals, zoanthids, and sea cucumbers are also present. Access is by boat only, with mild currents and visibility between 10 and 30 metres. Hazards include overhead environments, sharks, sharp coral, strong currents, and surge.

Sairee Reef, located off Koh Nang Yuan, provides a shallow, accessible environment for beginner divers. The site features depths between 5 and 12 metres, averaging 8 metres, with mild currents. Visibility varies from 5 to 25 metres. Divers can observe wrasses, which are common, alongside uncommon species including golden butterflyfish, longfin bannerfish, blue-barred parrotfish, coral trout, pink skunk anemonefish, rock cod, rabbitfish, sergeants, hard coral, and snails. Entry is from the shore, though divers must navigate a shore break and watch for active boat traffic. Using a surface marker buoy is recommended for safety. The site is suitable for night diving, with water temperatures consistently ranging from 28C to 31C.