As the weather heats up, the number of bull shark sightings up and down the Brisbane River is also on the rise.
Anglers, rowers and recreational boaties have all reported more shark activity from the city reaches to the banks of the Bremer River in recent weeks.
"It's not just the Brisbane River, but also the Logan River; all tributaries that run off the east coast of Queensland and northern New South Wales are loaded with bull sharks," local expert Paul Burt said.
"Dusk and dawn is when these sharks feed and hunt all the way up the river to Moggill Ferry.
"We're talking three-metre sharks swimming up the river."
Mr Burt said he was not surprised by the increase in local sightings.
"The bull sharks have always been there under the water," he told ABC Radio Brisbane's Rebecca Levingston.
"This is the time of year when bull sharks are active as the big females go upstream to lay their pups.
"We're seeing them more now with drones and people actively looking for them."
Rower's scull attacked
A young rower had her scull attacked at the weekend while training near the Kurilpa Bridge in the CBD.
Coach Peter Toon said teeth marks were left on the rower's craft after the attack.
"She saw the fin and it went around and gave it a big snap on the stern of the boat," he said.
"It put some big gouges into it and it upset her quite a bit as you could imagine."
Mr Toon said despite the scary incident, the rower had been back on the water this week.
"I've been coaching for over 25 years and I've never heard of an incident where a bull shark has attacked a rower."
Poor eyesight, good vibrations
Despite bull sharks having poor eyesight, Mr Burt said the receptors on their heads picked up vibrations in the water.
"The shark goes left to right and it sends out a sonar which tells him where to move until he hones in on the vibration," he said.
"Usually it's a mullet or other fish but it could be a paddle going into the water, and that's the problem — they come up and take a bite."
Mr Burt said bull sharks were opportunistic feeders and often took a bite out of something before realising it was not what they wanted.
"The unfortunate part of it, especially if a human being is involved, is that they can suffer a nasty gash that can lead to blood loss and drowning."ABC