Excitement is brewing that Migaloo, the world-famous white whale, may have been spotted again for the first time in five years. The humpback had been a regular visitor to Australia since 1991, when he was spotted in Byron Bay, and he's believed to be around 38 years old.

What's remarkable about the new potential sighting is that it was made off the coast of New Zealand's South Island, close to where he once ventured a decade ago.

Georgia Phelps, the UK-born manager of New Zealand's Mangamaunu Retreat, shared a series of photos with Yahoo News showing a white whale swimming along the Kaikoura Coast.

Before her mate, Abi, messaged her about the strange whale on Friday evening in a group chat, she'd never heard of Migaloo. "I didn't even know white whales existed. So I grabbed a camera and went for a drive," she said.

The whale's appearance was so distinct, Georgia and Abi began searching for similar sightings online and stumbled across the name Migaloo.

The women's excitement has been shared by international whale experts and media outlets on both sides of the "ditch". "My phone has been going crazy, I can't believe it. It's so exciting, and great to have good news for a change," Georgia said.

For around two hours, they watched the white whale swim with a pod of five to eight more whales, around 300 metres off the coast. "It was, it was just a really nice, wholesome feeling that it was something incredible that you never expect to see," Georgia added.

Whale experts around Australia had hotly debated what happened to Migaloo. Some feared the worst, but others noted that whales commonly stray from their regular migratory routes. In July, the vice president of Organisation for the Rescue and Research of Cetaceans in Australia (ORRCA), Steve Trikoulis, described his disappearance as a "mystery".

On Tuesday, Macquarie University whale expert Dr Vanessa Pirotta, said she'd always felt "optimistic" about Migaloo still being alive.

Most of the so-called white whale sightings that she sees are actually just pictures of them upside down, exposing their pale bellies. But in Georgia's photos, you can clearly see his dorsal fin and mouth.

"It makes the case for a really strong likelihood this could be him," she told Yahoo.

While white whale sightings are rare, two calves with light colouring were spotted in Tonga last year, and another one seen off the NSW coast earlier this year. Others have been spotted in South America and the Northern Hemisphere.

Dr Pirotta believes the photographs warrant further investigation, and she's calling on Kiwis to report any sightings to local authorities. It's unknown whether the humpback is still in New Zealand waters or whether the whale is drawing closer to Antarctica, because sometimes they can cruise at over 14km/h, and other times they will stop and feed.

Pirotta dedicated a chapter of her book, Humpback Highway, to Migaloo and she's clearly invested in his welfare. But she's working to evaluate the sighting as a scientist.

"With my science hat on, I always make sure I'm not overstating what could be. But as a general human being, I'm incredibly excited," she said.

Frenzy of excitement after world-famous discovery off coast