Hells Gates is the narrow entrance to Macquarie Harbour, named by convicts bound for the Sarah Island penal settlement. The harbour drains a huge catchment of tannin-stained water through the gap, and breakwaters built in the late 1800s and early 1900s to train the channel have created shifting sand spits either side.

The Marine Life Network guide describes the SS Devon (1894), stranded on the South Spit and now mostly buried by sand behind the breakwater, with her stern and steering gear visible at low water in 2-3 m, and the SS Kawatiri (1907), thrown against the breakwater and onto the North Spit (now Kawatiri Shoal) in 2-4 m. It rates the Devon as an interesting snorkel with occasional strong currents, and the Kawatiri as worth a look only on an exceptionally calm day because of freak waves. Visibility is limited by the dark harbour outflow.

Tasmania's west coast faces the full Southern Ocean, and the Marine Life Network guide notes that most of it is diveable only after easterly winds have flattened the swell - an uncommon event largely confined to summer. Macquarie Harbour and Cape Sorell provide the only reliable shelter from south-westerly swell. Crayfish grow large here, abalone are common and fish life is thin on exposed reefs, which are battered by constant swell.

There is no dive shop, air station or chamber anywhere on the west coast; the nearest hyperbaric chamber is the Royal Hobart Hospital, about 4 hours from Strahan by road. Every west coast dive should be treated as remote: carry oxygen, a radio and an EPIRB, and have a realistic evacuation plan.

Strahan is on Macquarie Harbour, about 4 hours from Hobart via Queenstown or 3 hours from Devonport/Burnie via the Murchison Highway. Boats launch at the Strahan ramp and run about 30 km (45-60 minutes) down the harbour to Hells Gates, the narrow, tide-swept entrance at the harbour mouth. The entrance is notoriously dangerous: strong tidal streams, a shallow bar and freak waves.

Cross or dive it only in calm conditions, near slack water, with a seaworthy, preferably self-draining boat, and check MAST advice. Macquarie Heads also has a campground reached by road from Strahan (about 15 km), from which the South Spit and breakwater area can be viewed.

Hells Gates faces the open Southern Ocean to the west; any westerly or south-westerly swell produces breaking waves across the bar and entrance. Tidal streams run hard through the 120 m-wide gap and outflowing tannin-stained harbour water reduces visibility, especially after rain and on the ebb. Only dive in rare easterly weather with minimal swell, at slack water.

There is no general dive at Hells Gates itself; divers visit the shallow wreck sites inside the breakwaters (SS Devon on the South Spit, SS Kawatiri on the North Spit) at slack water in exceptional calm, snorkelling or diving in 2-4 m.

No dive operator on the west coast. Air and gear must come from Launceston, Burnie/Devonport or Hobart (the regional guide notes locals sent tanks overnight to Burnie for fills). Sites are dived only by self-sufficient private boats and abalone divers.