Kangaroo Island tour guide Nikki Redman was excited to see a pod of three whales at Cape de Couedic on the southwestern tip of Kangaroo Island on Saturday.
Little did she know the significance of her observation, as the three whales have since been identified as blue whales by the experts, probably on their migration westwards.
Thinking they were southern right whales, Ms Redman sent her photos to the SA Whale Centre and Encounter Whales' Elizabeth Steele-Collins, who realised they were the much rarer blue whales.
Ms Steele-Collins, only a little envious, joked she was going to have to move to Kangaroo Island so she could see a blue whale.
Dr Pete Gill, CEO of Blue Whale Study, has spent a lifetime studying blue whales and said it was a real treat to see a pod so close to shore.
The blue whales off Australia are actually the pygmy blue whale subspecies.
Although at an average of 25 metres long, they are not much smaller than the full-size Antarctic subspecies, which at 30 metres long is the world's biggest animal.
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Dr Gill said blue whales were known to frequent the eastern Great Australian Bight, which was an important feeding area, all the way south of Kangaroo Island around to Robe and King Island.
But there were usually seen at least 20km out to sea on the edge of the continental shelf.
The whales at this time of year were known to migrate westward past Bremer Bay, around the southwest corner of Australia, up to tropical Indonesian waters where they overwinter and breed.
Dr Gill said it was possible these three blue whales came together as they rounded Kangaroo Island on their migration.
All three whales from Ms Redman's photos appeared to be adults, he said.
"While they are most often seen singly, they do have great big booming voices and can communicate over 10s of kilometres," he said.