Holly Coffey is no stranger to making waves.
She formerly did so while carving up the sea on a surfboard, and now - while recovering from an injury - by posting cheeky snaps on Instagram.
The most recent posts from the 20-year-old however, have raised more eyebrows than usual, and not for the reason you would think.
The series of posts showing off a set of itsy-bitsy fluro bikinis from Fashion Nova may have flashed a whole lot of skin, but it was what was on that skin that got an unusually strong response.
The thin tan line stretching around Holly's hips has sparked a borderline panic in the comments section, with fans losing their minds over the origin, identity and solution to the visible lines.
Only adding to the mystery, is the fact her sister Ruby has the exact same tan line.
"Confused by your tan lines lol," one fan commented on a series of very hands-on shots with Holly's boyfriend Jesse Weaver.
Others quickly followed suit.
"That tan line tho," one agreed, alongside a red 'x' emoji.
"What is the stripe on your ass?" another bluntly asked.
It quickly descended into a full-blown investigation with several fans determined to get to the bottom of what I'm calling tan-gate.
"We need to see what makes that tan line!" was the call to action that galvanised a torrent of guesses.
"Holly probably wears wicked weasel bikinis," one sleuth deduced, referring to the 'micro' bikini available from the retailer.
"Fake tan line?" another guessed.
Finally, a Sherlock Holmes figure came to the rescue with the most likely explanation.
"Did people ever think that maybe her tan lines are normal to where she wears her bottoms she just pulls up the bottoms for the photos?" they wrote.
The photos raised some eyebrows for their risqué content, but hilariously the surfer's tan lines were the main focus of the investigation.
A family of surfers and swimsuit models
Formerly ranked in the top 100 in the surfing qualifying series, Holly has also built up a following just shy of 1 million on Instagram.
Along with her sisters Ellie, Ruby and Bonnie, Holly's Instagram feed mixes professional surf shots with bikini modelling.
The mix of the two may have nabbed the ladies an impressive number of followers, but it’s also come with its share of negative commentary - and not usually tan line related.
The sisters shrug it off however, telling Yahoo Lifestyle that the negativity doesn't affect them, and that embracing their femininity online is about more than just likes, it's about making a statement.
“For such a long time in the surfing industry, it’s been so male-dominated where women were expected to talk like a guy, act like a guy surf like a guy,” older sister Ellie said.
"Why can’t we post sexy photos in bikinis and be taken seriously, why does that take away from anything?” Holly agreed.
Got a story tip or just want to get in touch? Email us at email@example.com
Or sign up to our daily newsletter here.