YOU can't see them, but when the fish you snagged comes up missing its body you know they are there.
The water has been pretty dark and murky lately but residents reckon "hundreds of bull sharks" have been frequenting Northern Rivers waterways and beaches.
Staff from Brunswick Heads BP said sharks had been taking jewfish from unsuspecting fishermen casting lines off the breakwall.
"I was fishing down there and I saw it happen - a shark had bit a fish right up to the head," Caelan Ryan said.
"The water is pretty brown so unless they are right there in front of you, you won't see it."
Matt Hardy from Bruns Beach, Bait & Tackle said late last week he had reports of jewfish getting chomped on.
"Apparently the boaties down at sea, their mackerel have been bitten in half too," he said.
"It was all the freshwater coming out that's washed the (sharks) out.
"We've had low highs and higher lows and the fresher sea water isn't coming in as quickly but that will change towards the end of the week.
"The fishing has been great off the breakwalls.
"Fishers have been putting on a few tailor (as bait) and been getting a few chomps."
One Evans Head resident reported he went to the beach for a swim in Evans Head on the weekend but found Main Beach was closed due to a shark sighting.
Another local, Glenn Sanders, posted on Facebook: "Swum face to face with an 11' bull off the cape last week with my friend ... she had a sniff ... and let us go. (It was a) 250m swim back to the beach though."
Surf Life Saving officers said if there was a confirmed shark sighting, beaches would be closed if patrols were there. The beach would remain closed for 30 minutes after the last confirmed sighting for the animals to go further out to sea.
Department of Primary Industries Shark Smart advised on Saturday three bull sharks, which had been tagged earlier from being caught on SMART drumlines, were detected at Lighthouse Beach in Ballina, and another three on Sunday.
On March 7, five tagged bull sharks were detected at Main Beach in Evans Head, and one on March 8.
For shark activity and tagging head to @NSWSharkSmart on Twitter.
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