Click play to join journalist Aisha Dow on a boat with a scientist and a cynic as they make the amazing discovery.

KEITH Grigbsy knows Lake Hume.

The coastguard commander has been patrolling and fishing on the lake for more than 40 years.

So when The Border Mail asked him to pilot a boat so we could search for jellyfish, he thought April Fool’s Day had come early.

“When they told me about the jellyfish I said, “well, you’re going to have to pick me up off the floor, I think you’re having me on’,” Mr Grigsby said.

Russell Mason, the owner of The Compleat Angler in Lavington, knew it was no joke.

He’d seen them, he said, but he couldn’t believe his eyes when he saw them floating just below the surface while fishing a few years ago.

“We had the boat tied up to a tree. I looked down at the water, looked away, then looked again,” he said.

“Then I looked at the can in my hand to see what I’d been drinking.

“They were just drifting past.

“They’re in there but I’d be surprised if more than 1 per cent of the population knew.”

Another fisherman, David Mulholland, counted himself among the 99 per cent.

Then he was with a friend on the lake when they saw a 200-metre stretch of the jellyfish north of the Bethanga Bridge.

“The water was so clear you could see a metre into the water and see them,” Mr Mulholland said.

Having fished in the lake for 20 years Mr Mulholland thought he had a handy knowledge of its marine life but he had never previously seen jellyfish.

Contacting The Border Mail for some answers, the newspaper decided to investigate.

Enter the doubting Mr Grigsby and his boat as well as Murray-Darling Freshwater Research Centre invertebrate ecologist John Hawking.

Mr Hawking said he received a handful of reports every summer from those who had been surprised to spot the small, translucent creatures.

Out onto Lake Hume we headed on a perfect summer day.

And before long, there they were ... dozens of them, the size of 10 cent coins, floating serenely near the surface, north of Bethanga Bridge.

The freshwater species can grow between eight to 100 tentacles, though swimmers and skiers can be assured they pose no danger.

They feast on smaller prey.

“If you were a little zooplankton, I’d be a little bit worried,” Mr Hawking said.

Faced with a jellyfish specimen plucked fresh from Lake Hume, Mr Grigsby was finally forced to concede there are jellyfish in the lake.

It’s a find he believes will shock most of the lake’s regular users.

“I’ve been on the lake for about 40 years and I would have argued black and blue they weren’t here, but here they are,” Mr Grigsby said as he stared in wonder at the delicate white creature floating in a jar.

“They are beautiful.”