Turtle Gully is a Heron Reef site where a large gully leads out to a coral wall full of biodiversity, with scattered bommies at about 18 m beyond. The wall itself is best explored between 8 and 14 m, which keeps most of the dive at comfortable depth and makes the site suitable for all levels. Schooling unicornfish, spotted sweetlips and turtles are the regular highlights, and milkfish are often seen near the surface.

The wall is covered in hard and soft corals and hosts the full range of Heron's reef fish. The site has a local nickname, 'Harry's House', after a great hammerhead shark that has been known to approach divers here; sightings are occasional and not something to count on, but they are part of the site's reputation. Visibility is usually best on the incoming tide, and guides time the dive accordingly when they can.

The gully entry gives a sheltered start, and the wall provides easy navigation: out along it one way, back the other. Turtle Gully is in the resort's top ten, and it is a good all-round dive that combines wall scenery, fish schools and a chance of something big. Photographers will find it rewarding for both reef scenes and fish portraits.

It is also a good site for divers who are still building confidence, since the depth can be kept shallow while still enjoying the wall. Turtle numbers peak in the nesting season from November to March, when adult green and loggerhead turtles gather around Heron Reef before coming ashore to lay on the island's beaches.

Heron Island is 72 km north-east of Gladstone. Fly or drive to Gladstone, then take the Heron Islander ferry from the Gladstone Marina terminal (72 Bryan Jordan Drive; check-in from 7:45 am, departs 9:30 am on scheduled days, about 2 hours), or transfer by seaplane or helicopter. Dive gear is carried on the ferry in addition to baggage.

On the island, the dive centre sits beside the harbour; boats leave the jetty for three dives daily and most Heron Reef sites are 5-15 minutes away. Turtle Gully is about 10 minutes from the jetty on Heron Reef, dived from a mooring.

Heron Reef sites are chosen on the day by wind and tide. The prevailing south-east trade winds (strongest April-September, often 15-25 knots) make the southern and south-eastern reef edge rough, so the sheltered northern and western sites are dived most. Northerly winds in spring and summer reverse this.

The tidal range is up to 3-4 m and currents run strongly around the reef edge and through Wistari Channel on springs; visibility is usually best on the incoming tide. Cyclone season is November-April; summer storms and plankton blooms can drop visibility to 10 m. Stingers are uncommon this far south but present in summer.

Turtle Gully has its best visibility on the incoming tide.

Descend and follow the large gully out to the coral wall, then turn and follow the wall at 8-14 m with it on one shoulder. Make a short excursion to the scattered bommies at 18 m if air allows, then return along the wall and back through the gully.

Heron Island Resort Dive Centre is the only operator: three guided boat dives a day (about 9 am, 11 am and 3 pm) plus scheduled night dives, from the resort jetty; sites are rotated by tide and wind. Access requires a stay at Heron Island Resort (or the University of Queensland research station).