Billions of mysterious sea creatures have washed up on beaches along America's West Coast over the past few weeks.
The jellyfish-like creatures are known as 'by-the-wind sailors' or Velella velella and have stunned scientists as they are rarely seen.
Velella velella have been spotted along beaches from Oregon to Southern California, as well as on Canada's West Coast.
Kevin Raskoff, a professor of Biology at Monterey Peninsula College, told SCPR: "The numbers, if you extrapolate, are awe inspiring. With some of my students we counted more than a thousand per metre.
"The numbers get astronomical pretty fast."
Story continues below video...
Locals are puzzled by the unusual creatures too.
Andy Sway told SCPR: "They're beautiful blue, these circles with these clear fins that come up. I've never seen anything like it."
By-the-wind sailors float on the sea's surface and have a fin that acts as a sail so they can be transported by the wind.
Bader added that the unique creatures are actually "colonial organisms". They are not one main animal, but a colony of small animals that live together.
Velella velella do sting but are too weak to harm humans.
What is it? Terrifying mystery sea creature found in Borneo
Why did 220 manta rays wash up dead on a beach in Gaza?