There has been further scientific interest in a pod of Antarctic killer whales that were sighted recently off the New South Wales far south coast.

An Eden couple took photographs of the mammals while on a pleasure cruise off Eden's Twofold Bay.

Researchers identified the pod as a species that exclusively inhabits the cold, southern waters.

David Donnelly from the Dolphin Research Centre says the sighting remains a mystery.

"We have a pretty strong Antarctic convergence, which pushes up our east coast and hits that east Australian current and all sorts of animals appear," he said.

"I guess one of the amazing things is that in one small area of the Australian coastline we are known to have tropical species of fish and Antarctic marine mammals in the same region.

"It is unheard of."