Barrenjoey is the divers' name for Tenth Island, a low rock off Lulworth in Bass Strait. The Marine Life Network guide rates it 8 out of 10 as Tasmania's largest accessible seal colony, with 100-200 Australian fur seals, kelpies and schools of fish in shallow water of about 4 m. It describes the seals as playful and interactive, the smell as strong, and warns that pupping in late spring increases the shark risk.

The shallow depth allows long interactions with the seals, making this one of the best wildlife encounters in northern Tasmania for divers and snorkellers with a boat. Treat the depths, positions and conditions given here as a starting point, and confirm them with local divers and a depth sounder before committing to a dive.

The far north-east corner of Tasmania, from Eddystone Point to Cape Portland and Swan Island, is one of the most remote stretches of the state's coast. Roads north of St Helens and around Gladstone are partly gravel, the nearest shops are at Gladstone, Derby or Bridport, and there are no dive services at all. The Marine Life Network guide, written from the experience of Launceston divers, is still the only detailed published account of most of these sites.

Where Bass Strait meets the Tasman Sea around Cape Portland and the Swan Island group, tidal streams run hard, and the guide repeatedly stresses slack water, safety lines and experienced boat handlers for the wreck sites. The Royal Hobart Hospital chamber is five hours or more away by road, so any diving here should be conservative and planned with an evacuation route in mind.

Launch at the Lulworth ramp (about 1 hr north of Launceston via George Town and Weymouth) in good weather only, and run north to Tenth Island, roughly 20-30 minutes. Approach the colony slowly and do not land. There are no marinas or fuel on this coast apart from the towns named, so carry spare fuel, a VHF radio and an EPIRB, leave a trip plan ashore, and check MAST boating advice; many north-coast ramps are shallow at low tide, and a 4WD tow vehicle is a real advantage.

Tenth Island is exposed in Bass Strait to northerly and westerly weather and should only be visited in calm conditions. Pupping in late spring (November-December) increases the risk of sharks and makes seals more defensive. Use the Bureau of Meteorology coastal forecast for the North East Coast and Banks Strait, and check tide times for the nearest standard port before planning the run.

Drop near the colony in 4-6 m and let the seals approach; stay together, keep hands in, and avoid the haul-out rocks. 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 commercial operator. Dived occasionally by Launceston clubs and Tasmanian Divers (Launceston) groups, and by private boats and cray divers. Remote - full self-sufficiency required.