Bar crossings and tidal gates: Australia’s entrances explained

Much of the Australian coast is entered through sand. Rivers meet the sea across bars; bays drain through narrow, rock-bound gaps; and the tidal streams that make Yachtmaster theory so useful turn those entrances into gates that open and close twice a day. UK-trained sailors know harbours with walls; Australian sailors need to understand entrances with waves. This guide explains the mechanics and the local knowledge.

Why bars break

A bar is a bank of sand across an entrance, built by the river's outflow meeting the sea's longshore drift. Water over it is shallow. Ocean swell arriving from deep water slows and steepens as it shoals, and if the ebb tide is running out against it the waves steepen further and break. On the flood, with the current running the same way as the swell, the same waves stay unbroken. Hence the rules:

• Cross on the flood, ideally in the last two hours before high water, when there is most water over the sand and the current is with the swell.
• Choose the day with the least swell. Two metres from the south-east breaks most east-coast bars regardless of tide.
• Never cross on an ebb against a sea, and never at night if the swell is up, because you cannot see the sets.

Preparation

1. Get the bar report from the local Marine Rescue, Coast Guard or Volunteer Marine Rescue base by VHF or phone. They watch the bar daily and their advice is better than any chart.
2. Check the height of tide and the time of high water at the local secondary port.
3. Note the leads and waypoints. Several bars (the Wide Bay Bar above all) have published waypoints that are updated as the sand moves; the chart alone is out of date the day it is printed.
4. Secure the boat: hatches and washboards in, everything below stowed, crew in lifejackets and clipped on, engine running and checked, sails stowed or ready to drop.
5. Watch from seaward for ten minutes before committing. Count the sets. Bars are rarely uniform; you are looking for the gap between the larger groups.
6. Going in, keep the boat on the back of a wave, not the front; throttle to stay there. Going out, punch through between sets, bow into the waves, at a speed that keeps steerage without launching the boat.

The entrances to know

Queensland

• Wide Bay Bar, between Fraser Island (K'gari) and Inskip Point, the entrance to the Great Sandy Strait. Famous, wide, and crossed by a three-waypoint route published by the volunteer rescue base at Tin Can Bay. Straightforward in the right conditions; deadly in a big south-easterly swell on the ebb.
• Gold Coast Seaway: trained walls make it deep and usually easy, but an easterly swell against the ebb produces standing seas at the entrance. Busy with small craft.
• Noosa bar: shallow, shifting, not for keel yachts in any swell.
• Mooloolaba: trained entrance, generally safe, rough in a strong easterly.
• Bundaberg (Burnett River), Gladstone and the northern ports are deep-water and do not bar in the same way.

New South Wales

• Swansea (Lake Macquarie): a trained channel with a shallow bar and an opening bridge; settled weather only.
• Port Macquarie (Hastings River), Yamba (Clarence River) and Ballina (Richmond River): the classic mid-north-coast bars. Yamba is the deepest and most used; all three are watched by local rescue bases and all three close in a big swell.
• Port Hacking south of Sydney: shallow and shifting; local knowledge and a rising tide.
• Sydney Harbour, Pittwater, Port Stephens and Jervis Bay are deep-water entrances, though the Heads carry a steep sea on an ebb against swell.

Victoria and Tasmania

• Port Phillip Heads (The Rip): not a bar but the most serious tidal gate in Australia. Streams reach 8 knots over a rocky bottom between Point Lonsdale and Point Nepean; the ebb against a south-westerly swell breaks right across. Transit at slack water using the published predictions, keep to the shipping channel or the recognised yacht route, and expect pilot boats and ships.
• Lakes Entrance: a trained bar into the Gippsland Lakes with a strong ebb; watched by the local rescue base.
• The Tamar in Tasmania: a river bar off Low Head and 3 m tides with fast streams; entered on the flood.
• Hells Gates (Macquarie Harbour): a narrow, shallow gap on Tasmania's west coast with a wicked tidal race. Slack water and calm swell only.

South and west

• Backstairs Passage between the mainland and Kangaroo Island: a tidal race with overfalls when wind opposes tide. Timed on the stream.
• The Murray Mouth: not navigable by yachts.
• Mandurah, Bunbury and Augusta in Western Australia: entrances affected by ocean swell; local knowledge and settled conditions.
• Kimberley and Northern Territory straits (Clarence Strait, the Gugari Rip, the passages around the Vernon Islands): tidal gates with streams of 6 to 10 knots, transited at slack or with the stream, never against it.

How examiners use this

An examiner planning your exam passage will very often pick an entrance with a tidal or swell consideration and wait to see whether you plan for it. "When can we cross?", "what is the height of tide at 1500?", "who do we call for a bar report?" and "what is your abort plan if there is a set breaking across the leads?" are all fair questions. A candidate who says "we cannot cross until 1400 on the flood, and if the swell is over 1.5 m we go on to the next port" has understood the coast.