Bar Crossing Guide

Coastal bars are where Australian recreational boating does its most serious harm, and they are also the place where electronics help least.

That is not an argument against electronics. It is an argument for knowing precisely what they contribute.

#What electronics contribute

A verified depth sounder. Real-time measurement of the water you are actually in, which is the one thing no chart can give you. This only works if the offset is right — see depth sounders and transducers.

A saved track from a previous safe crossing. Useful context about where the channel used to run. Not a route.

Tide data, worked for the bar itself. See tides, currents and chart datum.

VHF, for the local log-on service and for local knowledge. See marine VHF and DSC.

A registered beacon, because this is a scenario where it may be needed. See EPIRBs and safety equipment.

#What electronics do not contribute

Where the sand is now. A bar is sand. It moves with every big sea. The charts guide point about survey age applies with unusual force: the chart is a historical model, and on a bar the model expires faster than anywhere else on the coast.

Whether it is safe today. No sensor aboard measures that.

Autorouting. A route generator has no idea a bar exists as a hazard class.

A bigger screen. Nothing about this problem is solved by display size.

#The physics worth understanding

Three things make a bar break:

Shoaling. Waves feel the bottom and steepen. Less water means it happens further out.

Swell period. A long-period swell carries far more energy and starts to break in deeper water. Two metres at fourteen seconds is a very different bar from two metres at seven.

Wind and stream opposition. An ebb running out against an incoming swell builds short, steep, breaking seas — the same wind-against-current mechanism the tides guide describes, concentrated into a few hundred metres.

Which gives the timing rule: cross on the flood or near high water slack, and treat a falling spring ebb against swell as a no.

#The procedure, in short

1. Tide, swell height and period, wind — together
2. Time for the flood or high water slack
3. Get current local knowledge
4. Log on where the service exists
5. Lifejackets worn. Gear secured. Hatches shut. Engine confirmed
6. Stop and watch several sets. This is the most valuable step and it is free
7. Decide — and be willing to decide no
8. Cross with purpose, on the back of a set, stern square, no turning in the break
9. Log off once clear
10. Note where the channel actually was

#The decision not to go

Every experienced bar operator has turned back, and the ones who have not are either very lucky or have not done it long.

Successful outcomes include:

• waiting four hours for the tide
• running to another entrance
• staying out overnight and crossing at dawn on the flood
• going home on the trailer from a different ramp

A bar does not care about your work on Monday. The pre-departure checklist argument applies here too: a threshold agreed in advance is far easier to honour than a judgement made when the crew is tired, cold and wants it to be over.

#Local rules and services

Bar crossings, lifejacket-wearing requirements and log-on services vary by state and territory, and some bars have specific local regulations. Confirm the current position with your state or territory maritime authority and the local marine rescue organisation — see safety equipment by state for where to look.

#Bottom line

Use the sounder, the tide and the radio. Ignore the chart's channel and the plotter's route. Watch the water for several sets, cross on the flood with purpose, and treat turning back as a normal part of the skill.