'Get out of the water as quickly and quietly as you can' - what to do if you encounter a shark in the water this summer

Labour Weekend didn't just see warmer weather for much of the country, it also saw plenty of sharks, including an attack off a Northland beach.

Department of Conservation marine scientist and shark expert Clinton Duffy spoke to TVNZ's Breakfast this morning about the attack in Northland and whether the warmer weather will see more of the predators in New Zealand waters.

"New Zealand averages, from over the last 25, 30 years or so, it's averaged about one attack every two years, so it’s a very, very low attack rate," Mr Duffy said.

He said the appearance of the great white shark off a Northland beach was consistent with normal patterns of behaviour.

"I've been studying them in Kaipara [and] Manukau harbours for a number of years and they’re reasonably frequent among that stretch of coast."

"Great whites are found all around the New Zealand coastline."

He said what attracts sharks to New Zealand waters is "lots of food, lots of fish".

"People think they feed primarily on seals, but they eat as much fish as seals."

Mr Duffy said we "don't really have a good handle" on whether warmer water temperatures affect sharks' patterns of migration.

"They tend to leave, or at least, certainly, a part of the population leaves every winter, heads up to the tropics and then comes back around this time of the year, but there's another part of the population, mainly the smaller ones, that seem to live here all year round."

His advice for anyone who may encounter large sharks is to treat any shark over 1.8 metres long as "potentially dangerous".

"If you don't know what species it is, you should just get out of the water as quickly and quietly as you can. You don't want to appear like you're wounded or struggling in the water.

"We're coming into shark season in New Zealand now. Quite a number of coastal sharks move in to shallow water at this time of year, and then they hang around to feed over the summer months. As the water warms up, there’ll be more and more sharks coming in close."