Great white sharks have been found with scars from gruesome bites, sparking speculation about who may be capable or game enough to attack the apex predator.
Photographer Euan Rannachan was cage diving with his friend and filmmaker Jalil Najafov in Mexico in August 2019 when a three-metre great white emerged from the inky blue depths with the scar that appeared like a massive bite.
Dolphins and Orcas have been known to kill sharks, but the teeth marks don't add up.
A fellow shark is far more likely to be responsible, with expert Julianna Kadar revealing cannibalism or aggressive mating habits could be behind the phenomenon.
"There are a number of reasons why sharks might bite each other including cannibalism, copulation and aggression," Ms Kadar — PhD Candidate at The Fish Lab at Macquarie University — said.
"It's common for larger sharks to cannibalise smaller individuals (and) during mating, the male shark usually bites the upper body or pectoral fin of the female to begin the copulation process.
"There are dominance hierarchies among individuals in a group of sharks that could certainly result in biting."
Mr Najafov posted a series of photos last year of one shark's massive set of what appeared to be gnarly "mating scars".
And rare fossil evidence found along the US coastline indicates ancient shark-on-shark attacks happened millions of years ago.
In four separate finds, fossil hunters and researches discovered ancient vertebrae of now-extinct sharks; all had bite marks.
Two even had teeth sticking out of them.
READ MORE: Day in the life of a man who tags great whites
'I can make out the teeth'
Mr Rannachan said he was stunned when he saw the bite on the huge great white, who has been dubbed Seabatch.
"Whatever bit this shark, it was huge," Mr Rannachan told 9news.com.au.
"I remember seeing it in the water and immediately realising I need to take a photo of the side of the shark before she left, because something did not look right
"The shark itself was a big one, so that bite is from something even bigger."
READ MORE: Deadly brown snake leaves behind 'rare' gift for snake catcher
Mr Rannachan had also suspected another great white shark was responsible for the scar.
"If I was to guess I would say yes (it was a shark). But honestly it's almost impossible to tell," he said.
"The fact there is no obvious bottom jaw mark would lead me to believe it's not.
"But looking close at the wound I can almost make out teeth."
Upon observing the photos taken by Mr Rannachan, Ms Kadar said a very large shark was likely responsible for Seabatch's wound.
"The pictured bite looks like it came from a large size individual," she said.
"The size of the larger shark could be estimated if the size of the smaller shark was known and even the species could potentially be determined."
