It's not a bird, it's not a plane, and it's certainly not one of those errant weather balloons so often blamed for UFO sightings.

According to Sydney UFO investigator Doug Moffett, a bizarre shining orb filmed hovering near Batemans Bay on the south coast late last month is a genuine unidentified flying object.

Eurobodalla resident Ben Roberts filmed more than eight minutes of footage early on June 21 tracking the bright sphere of light flashing and moving above the horizon.

He said he was "amazed" by how bright the UFO appeared.

"It was not a plane," he said.

"There were no flashes and it was way too slow. Same for a helicopter - no flashes and too slow."

That doesn't necessarily mean it was a spacecraft full of alien lifeforms paying south coast residents an early morning visit.

But Mr Moffett, an investigator from UFO Research NSW, said it meant there was no reasonable explanation.

"It doesn't fit any of the usual suspects, such as Venus, planes, weather balloons or military flares," he said.

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