Three Sisters on Michaelmas Reef is a Silverswift site and is not to be confused with the better-known Three Sisters on Milln Reef. Silverseries describes three isolated coral outcrops, bommies, that rise to the surface like a city skyline, located at the back of the reef and separated from the main lagoon, with depths to 15-20 m and visibility of 15-20 m. The image of a skyline is apt: from below, the three towers stand up from the reef slope into the bright surface water, with space between them for fish to school.

Schools of barracuda and trevally, and sharks, patrol around the bommies, and in the deeper areas coral trout and snapper hold station near the base. On the bommie faces, branching and plate corals and extensive hard-coral cover host nudibranchs, sea stars and moray eels, which peer from holes. Because the bommies are separated from the main lagoon, the water around them tends to be clearer than in the lagoon itself, and the site feels more like an outer-reef dive than its location, closer to Cairns than the outer reefs, might suggest.

Michaelmas Reef is a Marine National Park (Green) Zone, so fish populations are protected from fishing. The dive is straightforward: circling each of the three towers in turn, with depths easily adjusted to the group. It suits Open Water divers and is a good option when operators want a more sheltered or closer site than Flynn or Milln.

The bommie tops, reaching the surface, can be seen by snorkellers in calm conditions.

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 40 km out through Trinity Inlet and across the lagoon to Michaelmas Reef takes around 80 minutes on a fast catamaran and noticeably longer on slower dive boats or into a south-easterly chop.

Three Sisters is a Silverswift site on the back of Michaelmas Reef; it is unrelated to the Three Sisters on Milln Reef. 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 bommies sit at the back of the reef away from the main lagoon and are dived in normal trade-wind conditions; slack or a gentle current gives the best fish action.

Descend beside the first bommie, circle each of the three in turn at 10-18 m, looking to deeper water for coral trout and snapper and into the crevices for morays. Rise up the last bommie for a safety stop near its top.

Silverswift – occasional day-trip site; Michaelmas is also visited daily by Ocean Spirit Cruises (cay) and by Tusa Reef Tours; the mooring used on any day is chosen by the skipper according to wind, tide and other boats