Diamond Island sits just off Redbill Beach at the northern end of Bicheno and is joined to the beach by a sandbar that the Marine Life Network guide warns is dangerous to cross. The guide rates the diving 5 out of 10: reef and small boulders at 10-15 m, with many large banded morwong, and a kelp forest on the north-east side.

That kelp forest is a reminder of change on the east coast. The guide notes that the kelp disappeared in the late 1980s during an El Nino event and was expected to return; since then, warming water and urchin grazing have reduced giant kelp across eastern Tasmania, so divers should not expect the dense forest described in older accounts. The small boulders and reef still support banded morwong, wrasse, leatherjackets and crayfish, and the island's little penguins may be seen in the water around dusk.

Diamond Island is not a destination dive, but it is a reasonable alternative when the Governor Island sites are unsuitable, and a way to see a different part of the Bicheno coast. It is dived mainly by locals with their own boats.

Divers should be aware that the island is a nature reserve and landing may be restricted to protect the penguins and other seabirds. Because documentation is limited and the reef condition has changed since the published description, treat the details as a guide. A depth sounder helps locate the best boulder patches on the north-east side, and the skipper should keep watch for rips near the sandbar while divers are down.

Launch at The Gulch ramp in Bicheno (on the Tasman Highway, 2 hr from Launceston) and run north along the coast for about 2 km, roughly 5-10 minutes, to Diamond Island off Redbill Beach. The island is also visible from the Redbill Beach car park at the northern end of town, but walking or swimming out across the sandbar is dangerous because of rips and tidal flow, so the site should be treated as a boat dive. Diamond Island is a nature reserve with a little penguin colony.

Diamond Island is exposed to north-easterly and easterly swell, which also creates strong rips around the sandbar. It is diveable in westerly winds and small swell, and the north-east side gives shelter only from southerlies. Visibility drops after rain and southerly storms.

Avoid it on a strong NE sea breeze in summer afternoons; mornings are usually calmer.

Drop on the north-east side of the island at 8-10 m and explore the small boulders and reef towards 15 m, then return along the island's edge to shallower water for a safety stop. Stay away from the sandbar channel.

No regular operator. Dived only from private or club boats launched at The Gulch in Bicheno (e.g. Tas Uni Dive Club and Combined Clubs Weekend boats); the former Bicheno Dive Centre is reported closed.