The decision to close beaches during shark sightings is up to the surf lifeguards on the day, say Surf Life Saving NZ officials.

Swimmers were ordered out of the water at Waihi Beach about 1pm on Saturday after reports of a 50cm long baby shark close to shore.

Photo: File.

Lifeguards investigated and closed the beach after further reports confirmed a shark had been sighted in the flagged swimming area.

Surf Life Saving NZ Programmes and Services Manager for the Eastern Region, Mike Lord, says it is policy for lifeguards to close a beach if a shark is seen near swimmers or flagged areas.

'The policy is they will close the beach for up to an hour from the last sighting,” says Mike.

'We won't chase them away, it's their environment and it tends to aggravate sharks, which is not what want.”

'The policy doesn't really state a certain size. What we think about is looking after the swimmers. Obviously, if a shark is right in the flags, or going through an area of swimmers, the main thing is we don't want to alert them to a shark where there is potential for swimmers to panic and run out and get in way of shark.”

Sharks are common at this time of year across the wider Bay of Plenty coastline, but more sightings have been reported due to the clarity of the water, says Mike.

'We haven't had some of the major big storms flow through so the sharks can be identified a lot more.”

'It's been pretty small surf, you see them cruising up and down and the water's pretty warm this year as well.

'We are not shark experts if they see a shark sometimes it's pretty hard to tell what it is. The bigger the shark, the more concern people have. I wouldn't say the lifeguards close the beach all the time.

'It's completely up to the lifeguards.”

It is the second time in a month Waihi Beach has been closed due to a shark sighting. On Christmas Eve the beach was closed after a sighting of a shark in the flagged area.

But Department of Conservation shark expert Clinton Duffy told Fairfax Media lifeguards may be overreacting by closing the beach due to a 50cm shark.

He says the general rule adopted worldwide is that any shark above 1.8m should be considered potentially dangerous, if the type of shark is unknown, says Clinton.

"When they are getting to around 1.5 to 1.8m long, some of the species are getting big enough to inflict serious injury if they were to bite you."

Pauanui Beach was also closed last week due to a school of about eight to 10 sharks spotted.

Last week a bronze whaler was spotted out from Papamoa Beach. To read more about this click here.