Orca surround swimmer on pontoon at Wellington’s Oriental Bay

The man was stuck on a pontoon as the two orcas circled. Photo / Facebook

A casual late-night swim at Oriental Bay turned into a jaw-dropping encounter when Joel Crampton was flanked by two orca.

The encounter was caught on camera by a group watching from shore, who had been keeping an eye on the man as he relaxed on a pontoon in the middle of the bay.

In the footage, someone whistles to Crampton before jokingly calling out for him to jump into the water.

As the video draws to a close, a child asks what would happen if the figure on the pontoon did jump in, prompting a dry reply from another voice: “He’ll probably get eaten, Tom.”

An onlooker can be heard in the video pointing out an “oblivious man — just lying on his back”, moments before the presence of two orca becomes clear.

Since the start of the new year, Joel Crampton told Stuff he had fallen into a routine of heading down to the Wellington beach each evening.

“I swam out to the pontoon, like I’ve been doing most nights.”

Crampton told Stuff he had heard what turned out to be an orca surfacing for air.

He soon realised there were two of them, circling slowly around the pontoon.

“There was this big male with a big fin, and a female with a small fin.”

In a separate video, Crampton can then be seen swimming back towards shore.

The Department of Conservation said orcas are often seen in Wellington Harbour, particularly during spring and summer, as they hunt for stingrays.