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When Luka Radovic went out on his paddle-board, he didn't expect to come face to face with an orca.

The Auckland Grammar School teacher had only just set out from Kohimarama in central Auckland when he spotted a large pod of whales out towards Rangitoto Island.

Eager for a closer look, he joined a group of kayakers who were photographing the orcas about 100m from St Heliers Bay.

"I wanted to get close but I never intended to get as close as I did," Mr Radovic said.

The group was watching the pod from a distance when an orca rose out of the water right next to Mr Radovic.

"I couldn't stop my board hitting it. I didn't know if it would be startled and swim off or knock me into the water."

The whale swam alongside Mr Radovic's board, turned on its side and stared at him before swimming away.

"I nearly fell off my board in fright."

He said the trip back to shore was nerve-racking, "but in a good way".

"I was terrified but ecstatic."

Massey University marine ecology lecturer Dr Karen Stockin said orcas typically came close to shore to forage for stingrays all year round.

This often put them in direct contact with humans.

She said orcas were inquisitive animals and often approached people out of curiosity. Although wild orcas are known as "killer" whales, there are no reported incidents of their deliberately attacking humans.

They grow to about 7m long and usually live for up to 50 years, although some can reach 90 years old.

Fewer than 200 orcas are estimated to live in New Zealand waters.

Mr Radovic felt lucky to have had last weekend's close encounter with such a rare animal.

"I just think they're amazing creatures. To come that close to one was so exciting."

He said the experience only made him more keen to get back on the water.