A white humpback whale known as 'Son of Migaloo' has been spotted by whale watchers off northern New South Wales during the annual migration north.

Byron Bay local Alison Reid booked a whale watching boat trip in anticipation of spotting Migaloo, and was not disappointed when she saw a white whale.

She took photographs of the whale about 10am on Tuesday and watched him frolic with another humpback for about two hours.

"I cried. I screamed 'You gorgeous whale, thank you for being here for us today'," Ms Reid said.

"He's amazing. It was just an incredible sight, it was so unreal."

Son of Migaloo, swimming off Byron Bay on Tuesday, was first sighted in 2004. ( Supplied: Alison Reid )

Ms Reid said she had been an avid whale watcher for decades, but this was her first sighting of a white whale.

"I had the trip booked on the off chance we'd be able to meet with Migaloo.

"The conditions were perfect, the sun was shining, he came over to our boat, he came under our boat, the dolphins came in, it was truly incredible."

Sea World's Director of Marine Sciences, Trevor Long, spent about an hour on the water near the 'Son of Migaloo' and noticed the differences.

"I've been fortunate enough to have about six experiences with Migaloo," he said.

"Migaloo is a much larger animal, it's about 12 or 13 metres long, it's a fully grown adult.

"This animal that we've experienced today is much smaller, probably around 10 metres long."

Mr Long said Migaloo was first seen in Australian waters in 1985 and has a lot of skin damage from exposure to the sun.

"This animal doesn't have that same level of skin damage," he said.

"It's quite identifiable that it's more pure in its whiteness.

"This smaller whale was first seen in about 2004 and was last seen off the Gold Coast in about 2012."

Son of Migaloo the white humpback whale, with Mt Warning in the background. ( Supplied: Alison Reid )

The white whale was also spotted from Iluka in northern New South Wales on Monday afternoon, and off the Gold Coast shortly after passing Byron Bay.

The White Whale Research Centre recorded the first white whale sighting of 2016 off Port Stephens on July 22.

The famous whale Migaloo was first photographed in June 1991 off Byron Bay, and at the time was the only documented all-white humpback whale in the world.

The annual southerly migration of humpback whales usually occurs between September and November.