Wonder Wall is the outer edge of Upolu Reef and Ocean Freedom's second site on its Upolu day trips; Cairns Dive Adventures lists it as Wonderwall/Deepwater. Cairns Premier Reef and Island Tours, the operator of Ocean Freedom, describes reef walls covered in hard and soft corals, with diving at about 10-12 m, and bommies, coral outcrops, that extend to within a metre of the surface for snorkellers. Anemonefish, black-tip and white-tip reef sharks, turtles and schools of grazing fish are listed among the residents.

The combination of wall and near-surface bommies makes it a good site for mixed groups: snorkellers can float over the bommie tops and look down the wall, while divers explore the base and the faces. The walls are not deep by outer-reef standards, but their coral cover, including soft corals, is dense and colourful, and the edge position means more fish and more reef sharks than in the sheltered lagoon. Cairns Dive Adventures notes giant trevally, Maori wrasse and hawksbill turtles on Upolu, and all are possible here.

Depths top out at about 16 m according to reef-level data, so the site suits Open Water divers and confident beginners. Being on the outer edge, it is somewhat more exposed than the lagoon side and is best on calmer days. Upolu's proximity to Cairns, about 31 km, means shorter travel and more time on the reef, but visibility is typically 12-18 m and lower after rain.

It is the more interesting of Upolu's two main sites for certified divers.

Boat access only. Cairns day boats leave from the Reef Fleet Terminal (1 Spence Street) and the neighbouring Marlin Marina on the city waterfront, with check-in between about 7:00 and 8:00 am; most operators run transfers from city and northern-beaches accommodation, and there is paid parking near the terminal. The run of about 31 km out through Trinity Inlet and across the lagoon to Upolu Reef takes around 75 minutes on a fast catamaran and noticeably longer on slower dive boats or into a south-easterly chop.

Wonder Wall is Ocean Freedom's second site on its Upolu day trips; Cairns Dive Adventures lists it as Wonderwall/Deepwater. Enter from the stern platform.

The prevailing south-east trade winds (typically 15-25 knots from April to September) are what limit Cairns outer-reef diving: above about 25 knots trips may be cancelled, and exposed eastern moorings are used only in light winds. Summer northerlies are gentler but make north-facing moorings choppy. Box jellyfish and Irukandji are present from about November to May (stinger suits on every dive), and the cyclone season runs November to April, when a system in the Coral Sea can close the reef for days.

Visibility drops after heavy rain and strong winds; spring is usually calmest and clearest. Being closer to the coast, visibility is lower than on the outer reefs, especially after rain. The outer edge is more exposed than Upolu's lagoon and is best on light to moderate trade-wind days; in stronger winds operators stay in the lagoon.

Descend to the base of the wall at 10-12 m and follow it with the reef on one side, weaving around the bommies. Turn at half gas, rise onto the upper reef at 3-5 m for the return, and complete the safety stop over the bommie tops.

Ocean Freedom – daily day trips (paired with the Upolu Cay site); Upolu is also visited by Passions of Paradise (ExtaSea) and Reef Daytripper; the mooring used on any day is chosen by the skipper according to wind, tide and other boats