Dave McGirr was out walking his dog, Meg, along Criccieth beach near Porthmadog while on holiday in North Wales on November 13 when he made the unusual-looking discovery.
The retired sales director from Kinver, Staffordshire, has been visiting the area for the last five years, but had never seen anything like it before.
"I was picking up some rubbish and flotsam - to help keep the beach free from plastics etc - and noticed an unusual looking piece of driftwood halfway up the beach," he said.
"On closer inspection, it looked like some sort of shellfish that was attached to long tentacles of seaweed."
Dave is a keen photographer and always has his camera when walking Meg, so decided to use it to help him work out what they were.
"I took some photographs just out of curiosity with the intention of researching this when I returned back to our lodge," he added. "That’s when I found out that in fact, the tentacles and the shells were all part of the same creature and that they were gooseneck barnacles."
Gooseneck barnacles attach themselves to all sorts of objects, such as rocks, ships, ropes or flotsam floating out at sea. They filter feed on plankton and detritus and have a long fleshy stem that looks like a black neck which is topped, with a chalky white shell that houses the main body of the barnacle.
In some parts of the world such as Spain and Portugal they are a delicacy which can fetch around £80-£90 per kilo – or cheaper if frozen, and are said have a taste that resembles a cross between lobster and clam, with a texture similar to octopus. Some have suggested Dave's find is worth £4,000, or at least was.
"Apparently they’re quite rare and fetch a reasonable price for those that treat them as a delicacy," Dave continued, who posted his photo in a local Criccieth Facebook group as well as his own profile, where his wife Di proclaimed: "Aliens have landed!"
"But because they've been out the sea a few days they are not fresh anymore so they are not a delicacy anymore," Dave said.
"Someone said they may be poisonous if they are not fresh."
Since publishing his photo the story has gone across the country, leaving him "bemused" at how much interest his photo has generated, while another post in the Facebook group shared on Monday suggests the barnacles are still there.
When asked if he'd be up for eating one, Dave laughed: "I don't eat seafood. It would have to be on the Jungle (I'm A Celebrity) for big money."