As holiday makers enjoy the crystal blue water at Bill's Bay, in the WA tourist town of Coral Bay, fish skeletons lie scattered among the seaweed.
It's a stark reminder of Western Australia's largest fish-kill event in more than a decade and the epic effort locals made to save the beach before the peak tourist season began.
On March 27, the Department of Primary Industries and Regional Development (DPIRD), launched an investigation into the fish kill after an estimated 16,000 dead fish were counted along affected beaches on the Ningaloo Coast, including Turquoise Bay, Bill's Bay and Yardie Creek.
Bill's Bay, Coral Bay's most popular swimming beach, was the most severely impacted.
During this time, DPIRD warned people not the enter into or fish from the putrid water, which contained high levels of bacteria.
The analysis of water samples from Bill's Bay indicated no harmful algae were present, DPIRD said, but ammonia, nitrates and phosphates were detected, likely the result of decaying coral spawn and fish.
Marion Massam, from DPIRD, said the department believed the mass fish-kill event was caused by coral spawning.
"Coral spawn itself can use up oxygen in the water and when it breaks down, more oxygen is used up as part of the breakdown process," Ms Massam said.
"That reduces oxygen in the water for the fish. They can end up dying as a result."
Coral spawning is an annual event, which typically occurs following the March full moon, after corals are stimulated by the seasonal rise in water temperatures.
DPIRD said another factor which could have contributed was local marine heatwave conditions that occurred along the Ningaloo coastline in late March.
The department said the coral-spawn slicks could drift towards the shore and when trapped close to the coast, could create low oxygen conditions made worse by a low tide and swell.
The Ningaloo Coast is no stranger to fish-kill events. Authorities said the last fish kill of this magnitude was 12 years ago.
Beaches reopen to visitors
If you're travelling to Coral Bay these Easter school holidays, you can thank John Farne for the improved state of the beaches.
With a couple of trucks, a bobcat and a loader, John, his mates and the Department of Biodiversity, Conservation and Attractions (DBCA) took to the beach to clean up the dead fish, which were taken to the local tip.
"It was as bad as it gets and every year the coral spawns and you walk out and you go — sniff — 'Oh the coral is spawning' and that's the end of it. There's very little. But this year was the exception," he said.
"But as locals, we want to have it clean. We can't do much about the water but that's now freshened up. It's lovely out there so Easter school holidays, we're good to go."
On April 8, DPIRD removed the fish-kill alert for Turquoise Bay, Yardie Creek, Point Billie and Jane's Bay.
Sallyann Gudge, from the DBCA, said a survey of dead fish showed they were all reef-associated species and the ecosystem should recover soon.
"Fingers crossed that all those things fall into place and those fish numbers can come back. A lot of those fish species do recruit pretty quickly," Ms Gudge said.
Authorities say they will continue to keep a close eye on the Ningaloo Coast and the fish population.
DPIRD has reminded visitors to exercise caution in the area and not to enter or fish from any water that appears smelly and putrid, as it could contain high levels of bacteria.
They urge people to report any further fish kills to Fishwatch at fish.wa.gov.au or on 1800 815 507.
