Lego has been washing up on these beaches for 17 years

And they just keep showing up.

In February of 1997, the container ship Tokio Express was hit by a wave described by the captain as a "once in a 100-year phenomenon", 20 miles off Land's End in England. It tilted the ship 60 degrees one way and then 40 degrees back the other way. As a result, 62 containers were lost overboard - and one of them was filled with Lego.

4,756,940 pieces of Lego, to be exact.

While no one knows what happened next or what was in the other containers, what is certain is that these brightly coloured pieces of plastic from the container somehow escaped from the steel the container and began turning up on the beaches of Cornwall, Devon and even Ireland.

Coincidentally, many of the pieces were nautically-themed with octopuses, diver flippers and scuba gear being very common.

British writer and beachcomber Tracey Williams who runs the Facebook page, Lego Lost at Sea, has been collecting the pieces for years and post photos of the finds online.

She told the BBC that the most highly-prized items for beachcombers are the octopuses and the dragons.

"These days the holy grail is an octopus or a dragon. I only know of three octopuses being found, and one was by me, in a cave in Challaborough, Devon. It's quite competitive. If you heard that your neighbour had found a green dragon, you'd want to go out and find one yourself."

While it's a fun activity foer beach-goers, sightings of the Lego are also a useful way to track ocean currents.

US oceanographer Curtis Ebbesmeyer has been following the story of the Lego since it began.

"The most profound lesson I've learned from the Lego story is that things that go to the bottom of the sea don't always stay there," Ebbesmeyer told the BBC.

"The incident is a perfect example of how even when inside a steel container, sunken items don't stay sunken. They can be carried around the world, seemingly randomly, but subject to the planet's currents and tides."