Libby's Lair is a shallow dive on the far northern section of Heron Reef, built around numerous Porites pinnacles arranged in a maze-like pattern with smaller bommies scattered between them. Guides describe it as a great shallow dive that tends to have less current than many other Heron sites, making it a relaxed choice. The pinnacles are riddled with holes and crevices.

Morays live in many of them, cleaning stations operate in others, and larger fish such as triggerfish, coral trout and large red emperor move between the bommies. The site's signature resident is the flamboyant Elizabeth's chromodoris, a vivid orange and blue nudibranch that gives the site its name. The dive is essentially an exploration of the maze: divers move slowly from bommie to bommie, peeking into holes and looking for the nudibranchs and cryptic fish.

The shallow depth means long bottom times and good natural light, ideal for macro photography. Libby's Lair suits all levels, including newly certified divers, and is especially enjoyable for those who like hunting for small creatures. It is less about big animals than the cleaning station sites, although turtles and sharks can appear at any Heron site.

Divers should take care with navigation, since the maze of similar bommies can be disorienting; stay with the guide and keep an eye on where the mooring lies. The pinnacles are slow-growing Porites colonies, some likely centuries old, so fin contact does lasting damage; keep well off them and avoid kneeling on the sand close to their bases, where small gobies and shrimp live.

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. Libby's Lair is on the far northern section of Heron Reef, about 10 minutes from the jetty.

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.

Libby's Lair tends to have less current than many Heron sites and is sheltered from south-easterlies.

Descend among the Porites pinnacles and weave slowly through the maze of bommies, peeking into holes for morays and cleaning stations and scanning for Elizabeth's chromodoris. Keep track of the mooring direction and return through the maze for the safety stop.

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).