Margaret River local Sean Blocksidge has spent nearly two decades hoping to spot a rare and unique aquatic animal and this week he finally found one.

Key points:

 

• A WA tour guide has been searching for lampreys in the Margaret River for 20 years
• Sean Blocksidge finally spotted the prehistoric, eel-like creatures this week
• They are harmless to humans and travel along rivers at night

Lampreys are a jawless, eel-like fish that pre-date dinosaurs and are at risk of becoming endangered in Western Australia. 

Mr Blocksidge compared the long years he spent searching for a lamprey to searching for a yeti or a lochness monster.

He runs a tour company and was leading guests along the river edge when he spotted the lampreys in broad daylight. 

"I know this spot fairly well … a couple of lizards come and visit us pretty regularly," Mr Blocksidge said.

"And I looked down in the water, I was going to try and point out where some marron might be, and I was like, 'What the hell's that thing?'.

"Is that a weird stick? Is that lamprey? Please tell me that's a lamprey!"

Sean Blocksidge shared his photos on social media and was surprised by how many people were excited to see evidence of lampreys in Margaret River.(Supplied: Sean Blocksidge)

The long blue tube did indeed turn out to be one of these extraordinary aquatic species that ordinarily forage at night. 

"They’re kind of a bit legendary throughout the South West, you always hear people talking about them, but I've never actually seen one," he said.

"I think these things just fascinate me because they really are living dinosaurs, you know, hundreds of millions of years old.

"But yeah, unfortunately, they are quite hideous-looking creatures. I don't think people are as perhaps interested in them as they should be."

A lamprey is a prehistoric, jawless fish that uses a suction mouth and rows of teeth.(Supplied: Ted Lawrence Great Lakes Fishery Commission )

Mr Blocksidge said his guests thought he was probably losing his mind a little bit but they also appreciated the importance of the discovery. 

"I thought maybe I was slightly overreacting, then I chucked it up on Facebook and it turns out there are quite a few people interested in lampreys," he said.

"I think we're up to 80,000 on the post's reach this morning and a lot of comments and a lot of shares.

"A few people were happy to see that they're around, I went back late at night and found a few more so hopefully there are more than the dozen or so that we end up seeing."

Sean Blocksidge is a tour guide in the Margaret River region.(ABC News: Robert Koenig-Luck)

Stephen Beatty is a senior research fellow at Murdoch University and is passionate about aquatic ecosystems.

He was thrilled to see Mr Blocksidge's Facebook post reach so many people. 

"I'm really excited for him and it's great that he's increased the awareness of this pretty unique animal," Dr Beatty said.

"In terms of evolutionary significance, they're a pretty amazing animal and we're really lucky to have one of the species come up our rivers in the South West.

"We encourage people, parents and kids, to get out and grab a torch on rainy winter evenings — that's your best chance of seeing them."

Lampreys can be difficult to spot in our dark-coloured rivers but they are harmless to humans.(Supplied: Sean Blocksidge)