The Aquarium is the reef directly beneath and around the Lady Musgrave HQ pontoon, inside what marine life writers call probably the largest coral lagoon on the Great Barrier Reef. It is a shallow lagoon wall dive over a sandy bottom scattered with coral bommies, at depths of about 7-10 m, with visibility of 10-25 m. The site is used as an introduction for non-certified beginners and as a relaxed dive for certified divers.

Its star attractions are the turtle cleaning stations, where resident green, loggerhead and hawksbill turtles gather to have their shells cleaned by fish, giving excellent photographic opportunities. The lagoon also acts as a nursery within a nursery, sheltering large numbers of juvenile reef fish. Other residents include whitetip reef sharks, chromis, damselfish, Moorish idols, parrotfish and butterflyfish, as well as giant clams, blue linckia starfish, staghorn coral patches, sweetlips, goatfish, snapper, rabbitfish and groper.

At dusk, mandarinfish are occasionally seen, which makes the site especially interesting for overnight guests on the pontoon. Because it is sheltered by the lagoon, The Aquarium can be dived in conditions that rule out the outer reef, and it is also a very good snorkelling site from the pontoon. The whole lagoon is a Marine National Park (Green) Zone, so fish are unafraid.

It suits everyone from first-time divers to photographers, and it is where most visitors to Lady Musgrave spend at least some of their day.

Lady Musgrave Island is about 96 km north-east of Bundaberg and 59 km east of the Town of 1770. Lady Musgrave Experience departs 15-17 Marina Drive, Burnett Heads (15 minutes' drive from Bundaberg; parking at the marina) at about 7:30 am for a roughly 2-hour crossing to its pontoon in the lagoon; 1770 Reef Eco Tours leaves the 1770 Marina (free parking beside the marina cafe) for a roughly 90-minute run. Private vessels anchor inside the lagoon via the marked entrance channel through the reef.

The Aquarium is entered directly from the Lady Musgrave HQ pontoon's dive platform inside the lagoon; no further boat ride is needed.

The lagoon itself is diveable in almost any weather, but the crossing is open ocean and tours are cancelled when south-easterly trade winds exceed about 25 knots or the swell is over 2.5 m. Outer-reef drift sites are chosen by wind and tide: the northern and western edges shelter from south-easterlies, the southern ledges need light winds or northerlies. Currents strengthen on spring tides and the outer sites are run as drifts on either the flood or ebb.

Cyclone season is November-April; summer storms and plankton reduce visibility. Calmest seas are often September-November and March-April. Inside the lagoon the water is sheltered from swell and the site is diveable whenever the boat can make the crossing; visibility in the lagoon (10-25 m) is a little lower than outside.

Enter from the Lady Musgrave HQ dive platform, descend onto the sand at 7-10 m and follow the lagoon wall with it on one shoulder, visiting the turtle cleaning stations on the larger bommies. Turn at half air, return along the wall slightly shallower and finish the safety stop beneath the pontoon.

Lady Musgrave Experience runs daily tours from Burnett Heads (Bundaberg) aboard Reef Empress to its Lady Musgrave HQ pontoon, with certified divers transferring to the dive tender Underworld for the 'Adventure Outer Reef Double Dive'; overnight stays on the pontoon allow extra and night dives. 1770 Reef Eco Tours also dives Lady Musgrave from the Town of 1770. The Aquarium is used for introductory dives (no certification required with instructor), snorkelling and overnight guests' night dives.