Michaelmas Island guards the eastern side of the entrance to King George Sound, and its northern shore gives some of the most reliable reef diving close to Albany. The Marine Life Network's Albany guide describes North Michaelmas as a run of rock walls and small caves dropping from the surface to about 18 m, decorated with plate corals, gorgonian fans and sponges. Unlike the ocean side of the island, the northern face looks back into the sound and so stays diveable in most weather.

The character of the dive is classic south-coast temperate reef: granite and limestone faces covered in colourful sponges and ascidians, gutters lined with fans, and scattered patches of the flat encrusting plate coral that surprises visitors this far south. Cuttlefish are common, and large blue groper, kingfish and queen snapper cruise the reef edge; lionfish (the temperate red lionfish/butterfly cod type) are occasionally recorded. Harlequin fish, western blue devils, boarfish and schools of bullseyes shelter in the overhangs.

At the north-west end of the island there is a much shallower site, North West Michaelmas, where two limestone bommies rise from ribbon-weed seagrass in 1-6 m about 80-100 m off the cliff. It is a quick snorkel or a shallow second dive, and a good place to find squid and cuttlefish over the seagrass.

The island itself is a nature reserve with seabird colonies and a haul-out for New Zealand fur seals and Australian sea lions, so marine mammals sometimes turn up underwater. Michaelmas is usually combined on a charter with the Cheynes III wreck, which lies just off the western end of the island. The site suits Open Water divers and is a good introduction to Albany's temperate reefs before the more exposed Breaksea sites.

Albany is 418 km (about 4.5 hours) south-east of Perth via Albany Highway. Charter boats and private boats launch either from the Emu Point boat ramp (Emu Point Drive, 7 km north-east of the CBD, with a large trailer car park, toilets and a fish-cleaning station) or from the town ramp beside the Albany Waterfront marina in Princess Royal Harbour, which exits into King George Sound through the harbour entrance past Possession Point. Michaelmas Island is about 6 km south-east of Emu Point (10-15 minutes).

The North Michaelmas site is about halfway along the northern shore; the shallower North West Michaelmas snorkel spot is about 300 m from the western end, 80-100 m off the steep limestone shoreline. Anchor in sand clear of the reef. Landing on the island is not permitted without authorisation because it is a nature reserve with seabird and seal colonies.

King George Sound is sheltered from the Southern Ocean by Flinders Peninsula, Bald Head and Breaksea and Michaelmas Islands, which is why Albany can offer diving on days when the open coast is wild. North Michaelmas faces into the sound, so it is sheltered from the Southern Ocean swell and diveable in most winds except strong north-westerlies through to easterlies, which blow straight onto the shore. The North West Michaelmas snorkel is good in all but strong northerlies.

Summer afternoon sea breezes from the south-east are usually fine here. Visibility is generally better than on the Perth because the site is further from harbour run-off.

Anchor in the sand off the reef edge, descend to 12-15 m and swim along the foot of the rock walls with the island on one shoulder, poking into the small caves and gorgonian-lined gutters. Turn on air or at one-third and come back shallower along the top of the reef at 5-8 m, finishing with a safety stop over the reef.

South Coast Diving Supplies (Albany) – the town's dive shop; runs scheduled boat dives in King George Sound most weekends and on demand in summer/autumn, and issues HMAS Perth permits – Michaelmas reef sites are used as second dives and for training.