The Supermarket is rated 8.5 out of 10 by the Marine Life Network guide, which calls it one of Tasmania's most beautiful dives. It is an extensive sandstone reef about 500 m offshore north of Blowhole Creek, with a central wall about 4 m high whose heavily eroded face has unusual rock pillars supporting ledges. Thick gorgonian fans and ledges packed with anemones cover it, and Bass Strait fish - long-snouted boarfish, magpie perch and wrasse - are common. The site was discovered by Neale of King Island Dive Charters; it was once full of crayfish, although numbers had declined heavily. The guide warns that careless finning destroys the delicate gorgonians.

King Island's reefs are best known to divers for their crayfish, which grow large in the cool, nutrient-rich Bass Strait water, and for sandstone and granite ledges covered in gorgonians, zoanthids and sponges. The Marine Life Network descriptions date from when King Island Dive Charters operated from Grassy; with no current operator, these sites are now visited only by divers who organise their own boat, and fishing pressure has reduced crayfish numbers since.

Recreational rock lobster and abalone fishing in Tasmanian waters needs a licence and is subject to seasons, size and bag limits. The east coast around Grassy is the reliable side of the island when westerly swell closes the west coast, and the island's lack of a chamber means aeromedical evacuation for any diving injury, so conservative dives are the rule.

This is a site for self-sufficient visiting divers with their own boat and a local contact; there is no one on the island currently guiding dives here, and the position given is an estimate from the published description.

King Island is reached by air from Melbourne (about 50 minutes), Burnie/Wynyard or Launceston; there is no passenger ferry, so divers fly in and hire a vehicle at the airport near Currie. Currie, the main town, is on the west coast; Grassy (with its harbour and boat ramp) is on the south-east coast about 30 minutes' drive away. Roads to the coast are a mix of sealed and gravel.

The Supermarket is 500 m offshore north of Blowhole Creek on the east coast. Launch at Grassy and run north, about 15-20 minutes.

King Island sits in the path of the Roaring Forties, and its west coast (Currie, Netherby, Cataraqui, Brahmin) takes the full force of the prevailing westerly and south-westerly swell; these sites are diveable only after long calm periods or in easterly weather, which is most common in late summer. The east coast around Grassy is sheltered in westerlies and becomes the fallback. Strong tidal streams run around the island's capes after gales.

The south-west-facing reef is protected from the full effects of swell but remote from shelter.

Follow the 4 m wall along its length, finning carefully to protect the gorgonians, then explore the inshore rocks before returning. Turn the dive at half gas (thirds where current or overhead sections are involved), deploy an SMB before surfacing for the live-boat pick-up, and complete a 3-minute safety stop at about 5 m where depth allows.

No dive shop or charter currently listed on King Island (Underwater Australasia has no listings); the King Island Dive Charters/Dive Centre referred to in older guides no longer appears to trade. Visitors must bring their own gear and arrange cylinders and a boat locally (hire weights/tanks on the island where possible to reduce air freight). Verify any current operator before travelling.