Wedding Cake Island is Coogee's landmark, a whitewashed lump of rock a kilometre off the beach that Midnight Oil wrote a song about, and it is the best boat dive in the central Eastern Suburbs. The island is about 150 m long north–south and 50 m wide, and it sits on a reef that falls away in a series of ledges and boulder slopes to sand at 20–22 m. The south-eastern side is the main dive.

Here a proper wall runs roughly east–west with its top at 15 m, undercut with small overhangs and caves, and beyond a flat section a second drop-off from 18 to 22 m runs out to the east. The whole system is covered in sponges, ascidians and soft and hard corals, and nudibranch diversity is high. Fish life is very good because the island is far enough offshore to be relatively untouched: wobbegongs under the ledges, yellow-banded seaperch, bream, snapper, old wife, blue groper, combfish, black reef and six-spined leatherjackets, cuttlefish, and above the wall rainbow runners and yellowtail kingfish in summer.

The shallows within 20 m of the rocks hold enormous schools of luderick and are a good place to finish. Eastern blue devilfish are seen under the deeper overhangs. Charter operators dive both sides and refer to the site as Wedding Cake North-West and South-East; the north-western side is a separate entry.

Because most of the dive can be done in 12–18 m with a shallow finish, it is suitable for Open Water divers with a few dives behind them, while the outer ledge gives advanced divers a 22 m option. Operators usually pair it with Magic Point or South Maroubra on a double-dive morning. Worth many visits; McFadyen first dived it in December 1990 and still rates it excellent.

Boat only. Wedding Cake is 8.5 km north of the Botany Bay northern headland and 10 km south of South Head – a 41 km round trip from the Cooks River ramp at Kyeemagh, or 30–40 minutes from Rose Bay. Pro Dive Coogee's boat runs from Botany Bay/La Perouse; Dive Centre Bondi and Frog Dive come south from the Harbour.

Line the right-hand side of the church spire above Coogee up with the left side of the large toilet block on the grassed area to find the south-eastern mark, or use the GPS, and anchor on the reef flat in 12–15 m south-east of the rocks.

The island stands in open ocean and takes swell from every direction; the trip is only worthwhile in relatively calm seas (under about 1.5 m) because both the run and the anchorage are exposed – St George Scuba Club cancelled repeated trips here in rough seas. The south-eastern wall is the lee side in north-easterlies and the worst side in a southerly, when the north-west side is used instead. At high tide the rocks barely show and swell breaks across them, so keep the boat well off.

A mild current may run along the wall. Visibility is generally good because the island is far enough from shore run-off; winter and autumn are best.

Descend to 12–15 m and head east to the main wall at 15 m; follow it north-north-east for about 100 m past the small caves, step out east to the 18–22 m drop-off, follow that ledge south examining the overhangs, then cut back west to the main wall and return. Finish with 10 minutes in the 5–8 m shallows towards the island for the luderick schools and a natural safety stop.

Pro Dive Coogee (most weekends, often as a double with Magic Point), Dive Centre Bondi, Frog Dive, Abyss Scuba Diving and Sydney Dive Academy; St George Scuba Club by private boat.