A New Zealand orca expert has lifted the lid on the mind-set of two orca captured on video yesterday, giving a pair of fun-loving Kiwi kids the fright of their life, as they swum off Waiheke Island's Enclosure Bay.

The man who took the video, Aucklander Shane Watt, told 1 NEWS the kids were "frozen" and "obviously very, very frightened".

"We were terrified just watching. It took us a minute to calm down afterwards so I can't imagine what the adrenaline would've been like for them."

Today, experienced marine guide and Whale Rescue co-founder Poppy Halliday said orca whales had good eyesight and were likely "echo locating".

"They realised they were two little humans and just kept moving," Ms Halliday told Stuff.

She said the pair were likely seeking out stingrays, among their favourite meals, and would have picked up the children's location from up to 80 metres away.

Ms Halliday described them as "curious" males.

It's the latest in a series of orca encounters this summer, with the marine animal enjoying our warmer waters after returning here for breeding.

Earlier this month, a trio of orca were spotted cruising along Papamoa Beach, much to the delight of beachgoers.

Late last year a stranded orca was helped out to sea by beachgoers, also at Papamoa.

An Akaroa jet-skier also received the surprise of his life with this encounter in Akaroa Harbour just before Christmas.