They are both winners of a junior surf competition in South Africa, but Ms Zoe Steyn won only half the prize money that her male counterpart received.
A Facebook photo of the pair holding up their winners' cheques has sparked criticism and accusations of sexism, after netizens noticed a huge difference in the prize money awarded out.
While Ms Steyn, who is from East London in South Africa, won 4,000 South African rands (S$395), her male counterpart Rio Waida from Indonesia won double that - at 8,000 rands.
Both are winners in the Under 18 men's and women's categories respectively, at the 2018 Billabong Junior Series Ballito Pro held in South Africa on Monday (June 25).
Comments critising the competition organisers came in fast, with one saying: "Wow! Blatant inequality Billabong... I hope your clothes are half the price for women if this is the case."
Another outraged commenter said: "Did the girls surf a different ocean that was easier we don't know about? This is pathetic."
In response, Ballito Pro said the prize money was determined by the World Surf League.
"The Ballito Pro maintains its stance as a pro-gender equality competition, which is evident from the ongoing development of the women's series year-on-year," said festival organisers.
"Based on this commitment to equality, we are meeting with all relevant stakeholders to discuss how any potential discrepancies can be resolved going forward."
The World Surf League also issued a statement in response on Wednesday, saying it has "instituted pay parity" in recent years at the Championship Tour level.
It added that it is still in the process of doing this for all other competitions.
Spokesman Will Hayden-Smith told ABC Australia that the disparity in prize money was partly due to the the number of entrants.
"Men get double the prize money only because there are double the competitors," Mr Hayden-Smith had said.
The competition had originally been planned for 32 men and 16 women competing for their respective titles. However, ultimately, only 24 male surfers and 14 women surfers competed, leading to a "subsequent pay disparty between the two events", the statement from World Surf League said.