A six-metre long whale shark has ventured far from home giving Rockingham swimmers a rare sighting.
It was seen swimming in Cockburn Sound on Thursday afternoon.
The whale shark is the largest fish in the world and usually inhabits waters more than 1000 kilometres north in Ningaloo, making this a very rare sighting for swimmers.
Rockingham Wildlife Encounters took to their Facebook page saying the experience took their breath away.
"Never has this occurred in over 30 years of operating! Seeing a whale shark as far south as Rockingham is as amazing as it gets!"
They said there was "nothing like experiencing breathtaking encounters with wildlife in their natural environment and to be part of unscripted events like this."
Murdoch University research fellow Dr Brad Norman said it was "very unusual" to have whale sharks so far south.
"But our previous satellite tagging program of whale sharks did track a couple of sharks as far as Rottnest," he said.
He said the shark spotted off Rockingham had not previously been recorded.
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"This is a great example of how the public can help research," Dr Norman said.
"A citizen scientist sent in ID images for review - I was able to process these images and run the ID scans - and we now have a new whale shark in the global photo-id database.
"Whale sharks are WA's Official Marine Emblem but there is still so much we're yet to discover about the biggest fish in the sea."
Dr Norman has previously spoken about using whale shark identification technology adapted from NASA's Hubble Telescope scientists to inspire and activate the next generation of citizen scientists.