The Blowhole is Lady Elliot's best-known eastern-side dive, an L-shaped cave with an opening at about 14 m that drops down and out through the side of the reef onto ledges at 20-22 m. It is the kind of short, open swim-through that gives an easy taste of cave scenery without a real overhead commitment, and it is too deep for snorkelling. Outside the cave, a cleaning station attracts silvertip sharks, and watching them come in to be cleaned is the highlight for many divers.

The wall and ledges are decorated with healthy gorgonian fans, and anemones with clownfish, angelfish, jacks and schools of fish fill the area. Turtles are common. The eastern side is the island's windward side, so the site is dived only in light winds or westerly conditions; when it works, it offers some of the most dramatic topography around the island.

The resort notes that the Blowhole, Tubes and Hiro's Cave are all accessible in a single dive, drifting south along the wall. The site suits divers with some experience and good buoyancy, ideally Advanced certification, because of the cave passage and the depth at the exit. Divers uncomfortable with enclosed spaces can swim over the top rather than through.

A torch is useful inside the cave and for bringing out the colours of the fans and anemones on the ledges. Because the eastern side is dived less often, the gorgonian fans here are large and in good condition, and fish are less accustomed to divers than on the western side, so approach slowly and keep bubbles away from the cave ceiling.

Lady Elliot Island is the southernmost coral cay of the Great Barrier Reef, about 80 km north-east of Bundaberg, and is reached only by the resort's light aircraft from Bundaberg, Hervey Bay, Brisbane (Redcliffe) or the Gold Coast (baggage limit about 15-16 kg, extra dive-gear weight bookable). From the airstrip, walk to the resort dive shop; boats are launched from the western beach or the lighthouse side and all dive sites are 10 minutes or less by boat. The Blowhole is on the eastern side of the island, a boat ride of up to 10 minutes; dived from a mooring when the east side is calm.

The island has a western (lee) side and an eastern (windward) side. Under the prevailing south-east trades the western sites (Lighthouse Bommies, Coral Gardens, the Severance) are sheltered and dived most days; the eastern wall sites (Blowhole, Tubes, Hiro's Cave) need light winds or a westerly/northerly. Swell over about 2 m from the south-east closes the eastern side, and strong northerlies (spring/summer) make the west choppy.

Tidal range is about 2-3 m; currents are strongest at the southern tip. Summer brings warmer water but more plankton and occasional cyclones (November-April). Eastern wall sites are dived only in light winds, westerlies or on calm days when the south-east swell has dropped.

Descend the mooring to the cave opening at 14 m, follow the guide through the short, wide L-shaped cave and exit onto the ledges at about 20-22 m. Watch the cleaning station outside for silvertip sharks, then drift south along the wall past Tubes towards Hiro's Cave, ascending gradually.

Lady Elliot Island Eco Resort's PADI dive shop is the only operator: guided boat dives twice daily (early morning and afternoon, bookings open the day before), plus courses; boat rides are 10 minutes or less and all sites are moored. Day-trip packages from Bundaberg, Hervey Bay and the Gold Coast include diving. The resort does not offer shore dives.

Dived when the eastern side is workable, often combined with Tubes and Hiro's Cave in one drift.