GAIN THE KNOWLEDGE AND CONFIDENCE TO AVOID A GROUNDING
The Gold Coast and Moreton Bay boast some of Australia’s most stunning waterways. However, these areas also contain some of the country’s shallowest waters, making navigation tricky. Moving through these waters without caution can lead to grounding, getting stuck, or worse. Outlined below are some essential tips for safely navigating these challenging waters.
KEY AREAS TO WATCH
Several areas require extra vigilance, particularly the southern end of the Broadwater. Straying outside marked channels here can leave you stranded on a sandbank in an instant. Many boats have run aground on the sandbar just south of the Couran oyster leases, in an area known as The Aldershots.
The oyster leases themselves pose another hazard. Their submerged structures can cause severe damage to boats, so extra care is needed.
Moreton Bay and North Stradbroke Island also contain perilously shallow sections, especially at crossings near Amity Point and Jumpinpin. Although local councils dredge these areas, shifting sands make it impossible to keep them consistently deep. For safer passage, use the Seaway whenever possible.
PREPARATION BEFORE SETTING OUT
Seeking advice from local boaters about safe routes and risky areas can be invaluable. Many new boat ramps, like the one at Southport, are designed for direct access to deeper waters, making them a smart choice for launching.
Checking the tides is crucial, particularly before heading towards the Seaway. Low tide exposes more of the channels, making navigation riskier. While high tide is generally safer, sandbars can still catch unsuspecting boaters off guard.
LEVERAGING TECHNOLOGY FOR SAFETY
Understanding where deep channels are is key to avoiding shallow water mishaps. If you lack extensive local knowledge, a GPS device with detailed maps and depth readings is your best ally. Additionally, carrying a physical Beacon-to-Beacon handbook provides a reliable backup to digital navigation tools.
Though depth sounders offer real-time readings, they are not foolproof. Often, by the time an alert is triggered, a boat has already hit shallow ground. Even advanced side-scanning transducers cannot ensure safety at higher speeds.
SAFE BOATING PRACTICES IN SHALLOW WATER
Speed significantly increases risks in shallow areas. When outside marked channels, keep your boat at a cautious six knots. Hitting a sandbar at high speed can stop your boat abruptly, potentially throwing passengers forward with force. While boats are built to withstand such impacts, passengers are not always as fortunate.
1. If you do run aground, follow these steps:
2. Turn off the engine immediately and assess the situation.
3. If you are seriously stuck, injured, or have sustained boat damage, call the Coast Guard or Volunteer Marine Rescue (VMR) for assistance.
4. If you are only lightly grounded, try trimming your engine to lift it clear and slowly easing off the sand. Avoid excessive power, as this stirs up sand and can damage your engine.
If necessary, have extra crew members disembark to help push and rock the boat while applying gentle power.
Always ensure your engine’s cooling system has proper water flow. Monitor gauges closely and check seawater filters for blockages. Boats with shaft drives require extra caution, as they are more prone to damage and harder to inspect without professional assistance.
Taking the time to navigate shallow waters carefully can save you from costly repairs and unnecessary risks.
UNDERSTANDING THE SHALLOW WATER EFFECT
A phenomenon known as the Shallow Water Effect (or Squat Effect) can make boating in shallow areas even more hazardous. This occurs when water is compressed between the hull and seabed, increasing the water’s flow speed under the boat and effectively “sucking” the vessel downward.
Effects of the Shallow Water Effect: reduced vessel speed; increased draft (the submerged portion of the boat); slower steering response; a change in trim, causing the bow or stern to dip. The best way to counter this effect is by reducing speed.
A notable example of this occurred in 1992 when the cruise liner Queen Elizabeth 2, with a draft of 9.8 metres, struck a rock at a depth of 10.5 metres while travelling at 24 knots. Investigators concluded that the Shallow Water Effect likely increased the vessel’s draft by between 1.4 and 2.4 metres, contributing to the accident.
By understanding this effect and adjusting speed accordingly, boaters can navigate shallow waters more safely and effectively.
Published in print August-December 2025
