A shark expert says the number of shark sightings this year is normal but warns sharks can attack because they're curious.
DOC marine technical advisor Clinton Duffy says shark sightings are common at New Zealand beaches and aren't something to be concerned over.
"When you're up in the air and any high vantage point you'll often see sharks at swimming beaches."
In late December, Duffy watched a two-metre Bronze Whaler swim past his wife and kids at Whananaki Beach but says it's a species he "wouldn't normally be worried about."
The country is on alert following the death of 19-year-old Kaelah Marlow by shark attack at Waihi Beach.
A 61-year-old man was also attacked by a shark last Saturday at Papamoa Beach. He was bitten while bodysurfing and left with puncture marks in his arm prompting a warning from DOC for swimmers to be vigilant.
There have also been several shark sightings over the summer including dozens of bronze whalers captured in an aerial shot at Matarangi Beach in the Coromandel.
Duffy says Bronze Whalers aren't "generally" dangerous but can get "wound up" near fish or fish blood.
"You wouldn't want to get bitten by one. They've got a good set of teeth, they're fish eaters, they get to over three metres long but they focus on fish."
He says sharks come close to shore in spring to "pup" and will stick around into summer to feed which is why sightings are more common during the warmer months.
People hitting the beach more could also be the reason for more sightings, but it's definitely not an increase in the shark population, Duffy says.
"Sharks live a long time, they grow very slowly, they reproduce slowly, so their populations don't increase very quickly and globally there are a lot less sharks around than there used to be."
While they do keep to themselves Duffy does warn of sharks attacking out of curiosity, as they attempt to figure out what is food and what isn't.
"Quite often you'll see white sharks swim up to things like seaweed, boxes, rubbish floating on the surface of the water they'll swim up and bite it to see what it is in case it's food," he says.
Duffy says sharks will also attack because they are hungry or feel threatened.
"They are actually scared of things that are bigger than themselves. They'll go through a display and tell you to back off if you don't back off, if you don't see it and don't realize what they're doing, then they bite."
He adds that the risk presented by a shark is dependent on the type, while a Bronze Whaler may not be much to worry over, a bite from a Great White would be "fairly devastating."
New Zealand and the east coast of Australia share a Great White population of 750, Duffy says they are considered endangered due to their natural rareness.
His advice for those who see a shark while out swimming this summer is to get out of the water quickly and quietly.
"It used to be the advice that you thrashed around and yelled and screamed but you're just making yourself look vulnerable."