Heron Bommie is the dive that made Heron Island famous and it remains the resort's signature site. It consists of six large coral heads that start in about 5 m of water and step down the reef slope to 18-20 m near the entrance to the harbour, and marine life writers routinely describe it as one of the most photographed dive sites in Australia. Each bommie is surrounded by branching coral forests, and together they act as a major cleaning station for the whole area: manta rays and eagle rays come in to be cleaned, clouds of damsels and anthias swarm over the heads, and cleaner wrasse service a constant queue of fish.

Batfish, Moorish idols, sweetlips, coral trout, trevally and barracuda are regular, moray eels peer from holes, and wobbegong and grey reef sharks are often seen resting or cruising the sand. The site also has famous residents, such as a large flowery cod known to guides as 'Fatty', and banded pipefish and nudibranchs for macro photographers. The fish density is exceptional because the whole of Heron Reef is a Marine National Park (Green) Zone and has been protected for decades.

The layout makes it ideal for all levels. Newer divers can stay on the upper heads at 5-12 m, while experienced divers can drop to the deeper bommies and wait at the cleaning stations for mantas, which are most frequent in winter. Photographers should plan several dives here to cover both wide-angle and macro subjects.

Because it is only minutes from the jetty and sheltered from the prevailing south-easterlies, Heron Bommie is on the schedule most weeks, and many divers dive it several times during a stay. It is also a common first dive for guests doing a check dive or refresher, and a good one to repeat on the last day before the no-fly interval.

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. Heron Bommie is the closest major site, about 5 minutes from the jetty off the harbour channel, and is dived on 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.

Heron Bommie is on the sheltered north-western side and is diveable in most trade-wind conditions; strong north-westerlies make it choppy. Current is usually gentle but can pick up near the channel on spring tides.

Descend the mooring to the shallowest coral head at about 5-8 m, then work down the chain of bommies to the deepest at 18-20 m. Pause at the cleaning stations and wait for mantas or eagle rays to come in, then zig-zag back up the slope between the heads, finishing the safety stop on the top of the shallow bommie near the mooring.

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). Heron Bommie is on the schedule several times a week and is the most requested site.