Severed feet encased in trainers have been mysteriously washing up along the coast of the Salish Sea between Canada and the US for the past decade, generating countless theories but no definitive answers.

Now the phenomenon is back in the headlines with the discovery of yet another disembodied foot — the 18th since 2007.

A man walking his dog made the lastest grisly found in British Columbia on December 8, according to the Royal Canadian Mounted Police (RCMP).

The pair were strolling on a beach in Jordan River, 30km northwest of Sooke on Vancouver Island when the animal came across the foot, with part of the leg still attached, inside a trainer, an RCMP spokesman said.

He called authorities, who sealed off the area and sent a coroner to seize the limb while a search was carried out, unsuccessfully, for the rest of the body.

British Columbia Coroners Services spokesman Andy Watson said a preliminary analysis indicated the remains were human.

There have been so many cases of pranksters stuffing trainers with animal remains like chicken bones over the years that authorities no longer make the obvious assumption.

The coroner will now work to determine the identity of the deceased, how the person died and whether it was accidental, a suicide or homicide, Watson told The Star.

The first severed foot was found on August 20, 2007. It was a right foot, size 12, encased in a shoe made in India. Authorities were able to link the foot to a male who suffered from depression, concluding he most likely committed suicide in or near water.

Of the 18 feet and shoes found, only two have been matched together.

On February 7 last year a hiker found a running shoe that contained a human foot in a sock at Botanical Beach near Port Renfrew. Five days later, a beachcomber found a second running shoe and contacted authorities.

The Coroners Service confirmed they belonged to the same person, but that person's identity is still not known.

The shoes were men's New Balance runners, size 12 and blue and black. This type of shoe was first sold in North America in March, 2013, which suggest the shoes' owner died at some point between March, 2013 and December, 2015, according to the Global News.

The Coroners Service has been able to identify eight feet that have washed up locally, linking them to six people. They do not believe any of the cases involved foul play. More likely the victims died from accidents or suicide.

That hasn't stopped people's imaginations running wild with grim theories about serial killers chopping up bodies.

"Some people do think [that]. Sad but true," BC coroner Barbara McLintock told Buzzfeed Canada last year.

"A lot of this is simply the quelling of the public imagination, to say 'No, this is unfortunate and they're all very sad cases'."

Forensic expert Gail Anderson said there was a simple reason why all of the cases involved trainers, not stilettos or sandals.

Air pockets inside the trainers make them buoyant, she said.

"It's basically a flotation device, so it's going to hold it all together and get it washed ashore," she said.

No foul play is suspected in any of the cases, and nothing has suggested otherwise.