Reports of "blokes being bumped" by bull sharks "on the chomp" in Gold Coast waters are emerging, prompting warnings that surfers should stay out of the water.
Brown and brackish floodwater is flowing from river mouths into popular surfing points following weeks of heavy downfall from Bundaberg to Sydney, but that did not stopped hundreds of surfers taking on big swells at point breaks on the weekend.
Daryl McPhee, an associate professor of environmental science at Bond University, said the flow of fresh water could not suit a certain predator better.
"Now it's a fantastic environment for bull sharks to be adjacent to river and creek mouths such as Tallebudgera, Currumbin and the seaway," he said.
"My suggestion is to put off [getting in the water] until things clear."
'On the chomp'
Surf reporter Terry "Tappa" Teece said there was an increase in bull shark activity over the week.
He said "blokes [were] being bumped" off their boards near Snapper Rocks.
"There's been quite a few around … they're on the chomp a bit," he said.
Teece said bull sharks were "like garbage collectors".
"They bump everything to find out if its a tasty morsel or not — and you don't want to get bumped," he said.
Dr McPhee said the conditions were making visibility difficult as sharks moved beyond their usual territory.
"Sharks don't have the best eyesight, but they do have seven senses," he said.
"One allows them to detect movements in very murky water.
"The good thing though is that most the time sharks know you're there and that you're not really food."
Dirt and debris
Beaches across the Gold and Sunshine coasts have been closed for weeks because of wild weather, poor water quality and hazardous surf.
Teece said surfers had been coming back in with headaches after swallowing dirty seawater.
"It's very dangerous for ear infections [and throat] infections," he said.
"It's very easy to get a throat or ear infection."
Dr McPhee said other health hazards, including E. coli and marine debris, were creating more problems.
"You expect to see gastrointestinal infections as well as an increase ear infections from entering floodwaters," he said.
"There are also quite a number of pieces still floating around … so hitting one of those while surfing or swimming is going to cause some significant damage."
