A 12-year-old boy who encountered a 3m-long mako shark at a popular Auckland beach says it was like "staring into the eyes of Jaws".
Safeswim issued an alert for Kohimarama and its neighbouring beaches yesterday following the sighting.
Keen sailors and twin brothers, Niko and Stavro Purdie, were sailing their Optimist yachts with their Kohimarama Yacht Club team, when they saw a large shadow.
At first, the sailors believed the shadow belonged to a dolphin.
But then Stavro had a close encounter.
"One of the kids said 'there's a shark behind you!' and then it hit my boat. Then I see this big grey shape that was three times the length of my Opti and it had a big fin."
He yelled out there was a shark, but people further away still believed it to be a dolphin, until about an hour later when they too observed it up close.
At that point, the yachts moved off into another area, and his coach pulled a swimmer out of the shark's path.
It was the first shark Stavro had seen in real life.
"It was like staring into the eyes of Jaws," he said.
"I count it as an experience, but not an experience I would really want to happen again."
Stavro said while it was a little nerve-wracking, he felt safe in his boat.
"Everyone in their sailing career encounters a shark or two.
"I'm just happy no-one got hurt."
Despite some of the team members expressing interest in diving into the water to swim with what they thought was a dolphin at that stage, Stavro took a safety conscious approach.
"I wouldn't go into the water with any big marine animals, because you don't know what it could be until it's eaten you or come up close to you."
Safeswim has since removed the alert.
Surf Life Saving Northern Region, which updates the alerts, said the shark had not been sighted again.
But its chief executive, Matt Williams, said swimmers should remain cautious of their surroundings.
"We have had a tragedy this year at Waihi Beach and I think that's increased the social anxiety and heightened the awareness around sharks," Williams said.
"We believe the sharks to be in the same areas and in the same number as they have been in previous years, and we're really wanting to encourage the public to be cautious but not lose sight of those more prevalent risks."
That includes not using equipment properly, taking pool floatation toys to the beach, getting caught in rips, fishing or exploring around the rocks, or wearing inappropriate clothing in the water.
"These are the risks 50:1 occurring at these coastal locations," Williams said.