Beam sea takes boaties by surprise

Lookout! Issue 32, December 2014 – January 2015

Two men in a small fishing boat had to make their way to shore through chest-deep water after their runabout capsized at the river mouth.
Choppy ocean waves
Maritime New Zealand ©2019
Looking along the seawall, the wave action can be seen at the entrance.

The boat’s owner had just finished getting it ready for the summer season and decided to take it out for a run. The sea looked calm, but as they moved out of the sheltered channel where they had launched and crossed into the river mouth, they found themselves immediately abeam of choppy ocean waves.

The skipper motored close to the shore for shelter, but they were still exposed and the last two of a set of swells broke on the boat and capsized it. The men ended up chest-deep in water and had to force their way back to shore through the surging water. While they made it back to shore unhurt, the boat sustained heavy damage.

LOOKOUT! Points

  • There have been several similar capsizes at this location, where a rigid wall divides the river into two parallel channels to protect the western bank from the ocean swells entering the bay. One channel leads past the wharf and out into the bay, and is mainly used by commercial vessels. The other channel is very sheltered and is used by recreational craft. Small vessels launch from a boat ramp approximately 500 metres upstream. As they exit the channel, boaties can find themselves suddenly abeam of the ocean swell and at great risk of swamping and capsize.
    • Local knowledge is invaluable when navigating tricky spots, but this can only be gained through experience, and through experienced skippers and crew sharing information and educating others.
    • Recreational boaties launching in unfamiliar waters should make it their responsibility to find out about any identified risks – in this case, the danger of a beam sea on exiting the channel – before they head out.
  • Conditions can change over time and at different times of the day. Sediment deposited from the river has lifted the seabed at this point, making the water more shallow and producing higher swells. This effect is more pronounced at low tide. The outgoing river flow opposes the ocean swell, making the swell face steeper at the channel entrance.
  • This incident demonstrates the importance of wearing a lifejacket on small craft in any conditions, because things can and do go unexpectedly wrong, even in what seem to be sheltered waters. There’s usually not enough time to retrieve lifejackets and put them on in an emergency.
    • The boat’s occupants, both grown men, were wearing lifejackets and made it to shore without further mishap. However, had there been any children or less able adults on board who were not wearing lifejackets, the story could have ended very differently.

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