John Totterdell was finishing a southern bluefin tuna survey near Cape Le Grand in Western Australia when an enormous icy blue shape emerged near his boat.
The lead researcher for the Cetacean Research Centre WA (CETREC) immediately recognised that a very special moment was about to play out.
Others aboard cheered and yelled as the world's largest animal finally broke clear of the ocean and pushed misty seawater from its blowhole.
"Wow, look at the size of that," one onlooker can be heard crying in footage of the encounter.
"Whoa, beautiful.
"A blue whale!"
Mr Totterdell guessed it was 18-20 metres long.
"[It was] just meandering around, wasn't in any hurry to go anywhere," he said.
"There's not a lot of water there — [it] is probably only double the length of the whale in depth, so it didn't have a long way to dive.
"We just observed it for a little while.
"It took several breaths and was just arcing around one of the islands there and heading towards another one."
'Quite significant'
The ABC contacted the Department of Biodiversity, Conservation and Attractions, which confirmed the animal was a blue whale based on its mottled grey colouration, head shape and blue hue prior to surfacing.
Mr Totterdell believes it might be the first recorded sighting of the species in the area.
"[I've] never seen one that close to Esperance — I've never seen one anywhere in the archipelago," he said.
"I've never heard a report of one … and I've been involved in the marine scene here for say, 40 years — so this is really quite significant."
He said if anyone had seen one inshore near Esperance previously, he would love to hear from them.
He noted blue whales were seen further out to sea and further west of Esperance, near Albany and Bremer Bay.
Pete Gill from Blue Whale Study in Victoria said the Esperance sighting was definitely an outlier.
"It's exciting to hear of a blue whale sighting in an area where it's rarely seen," Dr Gill said.
Unique pigmentation
After the sighting on February 14, Mr Totterdell said he sent photos and videos of the whale to other researchers in the hope they could identify the specific individual.
While some species such as southern right whales can be identified individually from the white bumps on their heads, he said blue whales could be identified by pigmentation patterns on their bodies.
"That pattern down its flank is unique to each of them," he said.
"[But] it's not something that you look at and go 'I know that guy!'
"You've got to really get in there and and go through your photos and study, so it might take some time before we know whether it's known or not."
Mr Totterdell said there was no evidence the Esperance blue whale was in distress and saw its presence as a positive sign.
He said numbers had been recovering since commercial whaling ceased and the sighting may be further evidence of that.
"It's just a sign these animals are becoming more plentiful, slowly," he said.
"We hope to see more of them."
