Bull sharks predominantly inhabit the warm, shallow waters along coastlines and river systems. Their preference for these environments makes them a familiar presence in such regions.

In terms of size, male bull sharks generally grow to about 2.4 meters, whereas females can achieve lengths of up to four meters, highlighting the noticeable size difference between genders.

Notoriously more aggressive than many shark species, bull sharks have a reputation for belligerence that even surpasses that of the famed great white shark.

Heavy rainfall contributes to an increased flow of freshwater into rivers and estuaries, which then merges with saltwater systems and beaches. This results in the creation of brackish water.

This brackish water is characterized by a mix of freshwater and saltwater, containing more salt than ordinary freshwater but less than that of standard seawater.

This is a phenomenon where fresh and saltwater mix, being saltier than normal freshwater, but less salty than typical seawater.

“Bull sharks are also one of the few species of sharks and rays that can tolerate brackish and even freshwater for extended periods,” Professor Jodie Rummer from James Cook University said.

“Which means they are especially comfortable moving in and out of river mouths and turbid coastal waters after heavy rain.”

The turbulent water conditions also flush out fish and other dead animals from rivers into open brackish water, attracting bull sharks to coastal regions where people may be more likely to be swimming.

“Analysis of bull shark catches close to shore always shows an effect of rainfall,” Professor Culum Brown from Macquarie University said.

“They are naturally attracted to these areas to feed.”

Is it safe to swim in Sydney right now?

Many beaches across NSW have been closed in the wake of the recent attacks, with experts urging residents to stay out of the water.

This is because the recent weather events are still having an impact on water systems across the state, and also make it murkier.

This means sharks’ ability to see and discern between prey and humans is lower.

“They will be attracted to disturbances in the water. They are more likely to accidentally bite a person, thinking it is prey,” Brown said.

“Given the incredible rainfall we have had of late, the risk of encountering sharks is high.

“Stay out of the water till it clears.”