"DON'T go swimming."
That was the advice from a fisherman on North Wall who caught a bull shark in the Richmond River this week.
The shark was about 1.5m long and was caught at the western end of the wall near the Shaws Bay caravan park.
And not much further along the wall, another fisherman had caught a bull shark of similar size.
The sharks were not released, but displayed as a warning to people that there are sharks in the river.
The river under Missingham Bridge is a popular spot for people learning to surf and for people on kayaks or stand-up paddle boards.
But the river has become murky with floodwaters.
Bull sharks are an aggressive species known to like dirty water.
They can grow to 3.5m in length.
These sharks can stay in fresh water for long periods of time to feed and breed.
Females sometimes give birth in river mouths where the young will live for up to five years.
Brett Hyde from Ballina Bait and Tackle said the dirty floodwater in the Richmond River at the moment was a "dinner bell" for predatory fish such as sharks and jewfish.
"A lot of fish get pushed to the river mouth with the murky water," he said.
"So that's when you start getting the sharks hanging around.
"Bull sharks in particular don't mind the dirty water, so this is the time to avoid swimming.
Wollongbar teenager Peter Edmonds lost his life in 2008 after being bitten by what was believed to be a bull shark while body boarding at Lighthouse Beach at North Wall.