Coral Canyons is a series of shallow canyons cut into the edge of Heron Reef, separated by coral ridges, with scattered bommies at greater depth beyond. The canyons are filled with fish, turtles and sharks, and the varied topography gives the dive a sense of exploration as you move from one canyon to the next. The site's signature sight is groups of bigfin reef squid hanging vertically stacked in the water column, rippling with changing colours as divers swim past.

The squid are most often seen in the canyons and near the ridges, and patient divers who stop and hover can watch them at close range. Each of the deeper bommies has its own array of fish and features, so the site offers something for divers who want to go a little deeper, while the canyons themselves are shallow enough for new divers. Turtles rest in the canyons and reef sharks patrol the edges.

Coral Canyons is in the resort's top ten sites and suits all levels. It is a good choice for divers who enjoy structure and animal behaviour, and it is excellent for photographers, especially for squid and turtle portraits. It was grouped with Coral Cascades in the earlier database pass but is a separate site with quite a different character: canyon topography rather than scattered bommies on sand.

The canyons also make a good late-afternoon or night-dive location when scheduled, as the squid, crustaceans and sleeping parrotfish are easier to approach in torchlight, and the shallow depth keeps the dive relaxed.

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. Coral Canyons is about 10-15 minutes from the jetty along the reef edge.

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.

Descend at the reef edge and explore the canyons one by one, swimming up each canyon and crossing the ridges between them. Watch for squid in the water column, then visit a deeper bommie or two at 14-16 m before returning shallower through the canyons.

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).