Three Sisters at Milln Reef features three distinct underwater structures comprising reef, pinnacle, and wall terrain. Divers and snorkellers can explore depths ranging from 5 to 30 metres, with an average depth of 26 metres. The site is accessed by boat, with mild currents making it suitable for drift diving. Visibility typically spans 15 to 25 metres. The topography includes walls anchored by gorgonian sea fans and sandy patches inhabited by garden eels. Mid-water columns host schools of fusiliers, snapper, and sweetlips, while the bottom is home to moray eels, lagoon rays, white-tip reef sharks, and sea turtles. Lionfish and stinging jellyfish may be present.

The Whale at Milln Reef is an intermediate dive site featuring a varied reef system that transitions from shallow coral gardens at 2 metres to deeper sections at 26 metres. Divers can explore the reef structure, which includes gorgonian fans in current-swept areas and ledges sheltering small groups of Harlequin Sweetlips. Marine life recorded at the site includes Whitetip Reef Sharks, Titan Triggerfish, and Emperor Angelfish, alongside common sightings of wrasses and Red Bass. Visibility typically ranges from 15 to 20 metres. Access is by boat only, and divers should be aware of sharp coral edges and potential jellyfish during the stinger season from November to May.

Milln Reef is an outer Great Barrier Reef site featuring a diverse topography of shallow reef tops, walls, and pinnacles. The reef starts at 5 metres and descends to 30 metres, with an average depth of 10 metres. Suitable for both divers and snorkellers, the site offers mild currents and visibility ranging from 15 to 20 metres. Access is by boat only, with typical dives lasting 45 minutes. The site is well-suited for beginners, though divers should remain alert to boat traffic during surface ascents. Water temperatures remain pleasant between 25C and 29C throughout the year.

Cathedrals at Flynn Reef features dramatic underwater architecture consisting of a wall and pinnacle structure. The site ranges from shallow reef terrain at 5 metres down to 30 metres, with an average depth of 20 metres. Divers encounter fan, plate, and staghorn corals across the formations. Visibility typically spans 15 to 20 metres. Access is by boat, and the site is suited for intermediate divers due to moderate currents. Hazards include sharp coral, sharks, and variable currents. Guided tours are available to assist with orientation and locating features such as giant clams. The site is suitable for night diving, with typical dive times around 40 minutes.

Boulders is a beginner-friendly boat dive located at Flynn Reef, featuring a combination of reef and wall topography. Divers can explore shallower reef sections starting at 8 metres, with the site extending to depths of 30 metres. Conditions are generally manageable, with mild currents and visibility ranging from 10 to 30 metres. Water temperatures remain warm throughout the year, fluctuating between 25C and 29C. When navigating the site, be aware of sharp coral and rocks near the wall. Divers should shuffle their feet when near sandy or rocky patches to avoid contact with stonefish, and maintain a safe distance from lionfish and sharks.

Ski Slope at Flynn Reef offers a varied profile, dropping from 5 metres to a maximum depth of 27 metres. This site features distinct reef zones and a wall structure, making it suitable for intermediate divers. Access is by boat only, with mild currents facilitating drift dives. Visibility typically ranges between 15 and 30 metres. Water temperatures remain warm throughout the year, though stinger suits are required from November to May due to seasonal jellyfish. The site supports a diverse range of reef fish and invertebrates across its multi-level topography. Guided tours and boat charters are available from Cairns and Port Douglas.

Magic Mushroom is a reef site located at Flynn Reef, offering shallow waters suitable for beginners. Divers and snorkellers can explore depths ranging from 5 to 15 metres, with an average depth of 10 metres. The site is situated 100 metres from the shore and experiences mild currents. Visibility typically ranges between 15 and 30 metres. Water temperatures remain warm throughout the year, fluctuating between 25 and 30 degrees Celsius. When entering or exiting the water, shuffle your feet to avoid sharp coral and rocks. Divers should remain mindful of hand and foot placement on the reef to avoid sea urchins.

Tennis Courts at Flynn Reef is a reef and wall site offering drift diving opportunities. Suitable for intermediate divers, the site features depths ranging from 12 to 25 metres, with an average depth of 20 metres. Visibility typically spans 15 to 20 metres. Divers should expect mild currents, which are best managed by drifting with the flow. Boat access is required for this site, which is located 20 kilometres from shore. Hazards include deep water, lionfish, sharks, and stonefish. Stinger season occurs from November to May, during which full-body stinger suits are recommended. Territorial triggerfish may be present during nesting season.