Christmas Island, off Mayfield south of Swansea, is rated 6 out of 10 by the Marine Life Network guide. Its lee side has sheltered shallow reefs, while its seaward side offers more adventurous diving, with depths of 2-12 m and a kelp garden at 6 m.

The guide lists 12 varieties of weed, leatherjackets, wrasse and velvetfish. It is a site for naturalists who enjoy temperate algae and small fish, and for divers staying at the Mayfield Bay campground. The lee side is gentle enough for snorkellers and new divers, while the seaward side is better left for calm days and experienced divers with boat cover.

The western shore of Great Oyster Bay around Swansea is a quiet stretch of coast known more for beaches, vineyards and the convict-built Spiky Bridge than for diving. Water inside the bay is often calmer but less clear than on the ocean coast, and several good sites are reached across private farmland, so local permission is part of the planning.

Practical points apply to all of these shore sites. There is no dive shop, air station or hire between Hobart and Bicheno, so divers bring filled cylinders and all equipment. Mobile coverage is generally good along the highway but patchy at the water's edge, and the nearest hyperbaric chamber is the Royal Hobart Hospital, one to two hours' drive away, so conservative profiles and oxygen in the car are sensible. Water temperatures range from about 11 °C in winter to 17-18 °C in late summer, so a 7 mm wetsuit with hood or a drysuit is standard year-round.

Christmas Island lies off the Mayfield area on the Tasman Highway south of Swansea. The Marine Life Network guide describes access by boat (Swansea ramp, 15-20 minutes) or an 800 m walk requiring landowner permission. Mayfield Bay has a public conservation area and campground.

From Hobart the route is the Tasman Highway (A3) via Sorell and Buckland; allow extra time on weekends when the road is busy with holiday traffic. Kit up at the car and check the entry and exit before committing, since the rocks are slippery at low tide.

The lee side is sheltered from most weather; the seaward side is exposed to easterly and north-easterly wind across Great Oyster Bay. Choose the side according to the wind. Mornings are usually calmest in summer, before the north-easterly sea breeze builds, and a day or two of westerly weather gives the clearest water.

Visibility of 5-10 m is normal.

Dive the sheltered lee side through the kelp garden at 6 m, or on calm days round the island to the seaward side for deeper reef to 12 m. 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 regular operator. Shore dives used by Hobart clubs (Tasmanian Scuba Diving Club, Tas Uni Dive Club) and self-sufficient divers; Hobart shops occasionally run east-coast weekends.