A "horrific" pool fault in Rio may have cost some Aussie swimmers Olympic gold.

We thought we’d reached peak pool disaster at Rio when the Olympic diving pool turned suddenly and inexplicably bright green.

But while the gross-out factor of green water is high, we’d wager many swimmers would rather take a dip in the murky depths than risk their chance at a gold medal.

A number of experts have warned that a current running through the 50m pool may have helped — or hindered — certain swimmers depending on which lane they swam in, particularly during 50m freestyle sprints.

According to three scientists — whose former peer-reviewed analysis also found a current influenced results at the 2013 world championships — swimmers in Rio in higher numbered lanes of the eight-lane pool performed better throughout the competition.

They noted that all but one of the eight men and eight women who swam fast enough in the semi-finals to qualify for the 50m freestyle final, swam in lanes 4 through 8, according to the Wall Street Journal.

In the final, a whopping five of the three male and three female medallists in the finals also swam in those lanes.


Aussie Cate Campbell swam in lane 5 in the 50m freestyle. Source: Getty

Gold medallist Anthony Ervin was the exception, swimming from lane 3.

"It’s a big deal. This is horrific,"  said Joel Stager who led the research.

The 50m freestyle is the only one-lap race in the Olympics, hence the only event where the advantage of a current wouldn't be evened out on a return swim towards the block.

In the women's final Australians Cate and Bronte Campbell swam in lanes 5 and 2, respectively and both failed to place.

While older sister Cate may potentially have benefited from the alleged current, her sister arguably wouldn't have.

The winner of the race, Denmark’s Pernille Blume, was in lane 4.

A current can be caused by a number of factors, such as the design of pool gutters, water return or lane ropes.

No swimmer has complained about such a current, but it is also unlikely they'd have felt it in the water.

The IOC has not commented.