A tropical cyclone making its way down the east coast could lead to swells of up to four metres in Gisborne on Friday.
Surf Life Saving NZ spokesperson Allan Mundy told Newshub surf clubs around Mt Maunganui were kept busy in the weekend as the swells overpowered even experienced surfers and swimmers.
The powerful swells were now on the way south and expected to hit Gisborne at the end of the week.
"Surf conditions aren't good when the water is behaving in this way - we had some rescues late on Sunday evening because people overestimated their ability."
Mr Mundy said the large waves could be very unpredictable and potentially life-threatening.
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He said volunteer lifeguards are only on patrol in the weekends, so people need to make sure they're staying out of the water until Saturday morning rolls around.
Mr Mundy also warned against walking along wet rocks, saying this could be a sign that a swell has recently hit the area.
"If you're down on the rocks and you see that they're wet, don't walk on them."
He said the swells in the Mt Maunganui area had died off early on Tuesday, and started making their way south.
"We're still cautioning people to stay out of the water 'til the weekend, when volunteers are able to keep an eye on things."
He said when the water gets too dangerous, lifeguards are instructed not to enter the water for rescue operations.
"First and foremost, we have to make sure the lifeguard is not in danger."
He said lifeguards are trained to deal with abnormal weather conditions, so if you see them avoiding the water, it's probably a good sign to stay out.
"You've got to think, if they're not even getting in, maybe you shouldn't either."