A viral video showing a saltwater crocodile swimming at a Cairns beach has locals scared to take a dip, but a wildlife expert says there's far worse things in the water to worry about.

The 10-second clip uploaded on Saturday shows the croc, affectionately named Snapper Jr, floating towards swimmers at Kewarra Beach before heading back to deeper waters.

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'Snappy Jnr' was spotted floating in the shallows at Kewarra Beach. Photo: 7 News

Reactions to the clip viewed more than 22,000 times have ranged from shock at the croc getting so close to shore and fears of ever stepping back into the water.

"That's insane!! Best video!! Should of thrown it a stick - it might have wanted to play 'fetch'?" Vera Moscardi said.

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Kewarra Beach, north of Cairns, has been the location for several croc sightings over recent years. Photo: Google Maps

"Deffs done with the beaches in Cairns! This was the only one I swam at, safe to say not anymore!" Raven Reeve said.

"And this is why you don't swim at the beach boys and girls!" Jess Fieldhouse said.

However, wildlife manager at nearby Hartley's Crocodile Adventures Drew Melville said there hadn't been any fatal crocodile attacks in the area for decades and that high-levels of box jellyfish posed a far greater threat.

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After being captured on camera, the crocodile swims away. Photo: 7 News

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