Image credit: ABC News

A rare blue whale was spotted off the coast of Australia Thursday for the first time in four years.

"The blue whale is the largest known animal ever to have lived on the Earth, which makes it absolutely amazing that we've seen one off Sydney," Geoff Ross of Australia's National Parks and Wildlife Service told the Sydney Morning Herald. "This is one of the very few confirmed sightings off Sydney. The last time one was seen off NSW [New South Wales] was from Botany Bay in 2008."

"I've been whale-watching here in Sydney for five years and I've never seen one," Jonas Liebschner of Whalewatching Sydney told the Australian TV channel Network Nine.

The giant whale was estimated to be 98 feet long and weigh almost 200 tons, the Associated Press reported.

Blue whales were close to extinction before a whaling ban in 1966, so this sighting may be a good sign for the recovery of the species as a whole.

"Today's sighting may be an indication that, like other large whale species, the blue whale populations are starting to recover after nearly being wiped out by whaling," Ross said.

The blue whale probably took a detour on its way to Antarctica, and was spotted by tourists on a whale-watching boat, according to the Associated Press.