Line Reef lies beside Hardy Reef in the complex of outer reefs east of the Whitsundays, with Heart Reef and Sinker Reef nearby. 100 Magic Miles describes it as a coral wall with small gullies and deep ledges, 3–25 m deep with 8–18 m visibility. Fish include cod, sweetlips, wrasse, coral trout and angelfish. What sets Line Reef apart is current.

The guide calls it strong and says the site makes a good drift dive, which is how it is best done: drop in up-current, ride along the wall and let the boat follow. The deep ledges give fish shelter from the flow, and as divers pass they look into overhangs where cod and sweetlips rest. The current feeds soft corals and brings pelagic fish along the wall.

Snorkelling is prone to current and best done as a drift too, with a boat following – not an option for inexperienced swimmers. For divers, Line Reef suits those with a little drift experience; Open Water divers can manage with a guide on a moderate tide, but it is rated here for Advanced divers or those with drift training. Line Reef is not on any day-trip schedule.

It is visited by liveaboards and charters working the Hardy complex, particularly those looking for drift dives. The channels between Hardy, Line and Sinker reefs concentrate tidal flow, so timing matters, and an experienced skipper is essential. Coral condition since Cyclone Debbie is not documented in the sources reviewed.

Divers who enjoy drifting should ask liveaboard crews about Line Reef, since it is one of the few documented drift dives in the Whitsunday outer reef.

Boat only. Hardy Reef lies on the outer Great Barrier Reef roughly 80 km offshore from Airlie Beach and Hamilton Island. Cruise Whitsundays' high-speed catamarans depart Port of Airlie (Airlie Beach) daily, with connections from Hamilton Island and Daydream Island, and reach the Reefworld pontoon in about 2 hours; scenic flights (about 30 minutes) also land at the reef by seaplane or helicopter.

Paid parking is available at Port of Airlie. Divers book certified or introductory dives on board. Other Hardy sites and the neighbouring Line, Sinker and Fairey reefs are reached by liveaboards and private charters; private vessels must use public moorings and observe no-anchoring areas.

Hardy and its neighbours are outer-shelf reefs fully exposed to the south-east trades (15–25 knots April–September). The large Reefworld catamarans run in most weather, but the crossing is rough in strong winds and diving can be restricted; smaller charter boats need a settled forecast. Hardy Reef's lagoon drains through a deep channel (about 60 m) beside the pontoon, and strong tidal currents run along the reef edges and through the gaps between Hardy, Line, Sinker and Fairey reefs, especially on spring tides and at the bottom of the tide – plan edge and wall dives for slack water.

Visibility is typically 8–20 m, up to 30 m on the outer faces. Marine stinger season (box jellyfish and Irukandji) runs roughly November to May – wear a full-length stinger suit or wetsuit with hood and gloves, carry vinegar. Cyclone season November–April; tropical lows and cyclones can close sites and damage coral (TC Yasi 2011, TC Debbie 2017).

Drop in up-current and drift along the coral wall at 10–18 m, looking into the ledges for cod and sweetlips; ascend with an SMB for live-boat pick-up.

No regular day-trip operator; visited on liveaboard/overnight dive trips from Airlie Beach and private charters. Cruise Whitsundays' Reefworld is nearby on Hardy Reef.