What are these mysterious objects appearing on beaches in Wales?

People visiting parts of the coastline in Wales have been spotting hundreds of bright blue, shimmering objects washed up on the beach.

Sightings have been reported in many places including Anglesey and Tenby with lots of pictures being shared online.

Some people have described them as "stunningly beautiful", "bizarre" or even like "alien jellyfish".

Experts say strong winds and sea currents are responsible for bringing the visitors to shore.

So what exactly are they?

They might look like rock or semi-precious stones but they are actually creatures known as by-the-wind-sailors, or velella velella in Portuguese.

They are usually only a few centimetres wide and look a bit like jellyfish, but are in fact groups of tiny animals living together.

Each has a little structure on top, like a sail, which helps it travel across the surface of the sea. The bright blue is a pigment that helps protect them from sunlight.

They are hydrozoans - tiny predators who live in groups in salt water, and are related to sea anemones and coral.

Marine specialist Frankie Hobro, of Anglesey Sea Zoo, said the creatures were "beautiful", but warned people not to touch them because of their sting.

By-the-wind sailors usually live in warmer waters, feeding on even tinier creatures, called plankton.

But scientists say windy weather can push large numbers of them onto the shore, creating what is called a "blue tide".

Frankie said the creatures usually come ashore in winter storms so aren't spotted by many people, and that June is "later in the season than expected to see them".

Experts are advising anyone who spots a by-the-wind sailor not to touch it as their tiny stinging cells can cause skin irritation.