You might have friends tweeting about or posting on Facebook pictures of blue sea creatures seen on the shores of California beaches. Some people have described these creatures as mysterious and bizarre but before you get caught up believing that these alien-looking creatures are from outer space, it is worth noting that marine experts are actually familiar of these unusual animals.

Marine scientists call this creature "Velella velella." The Scripps Institution of Oceanography of the University of California in San Diego, which is among the largest and oldest ocean research centers in the world, also said that this creature is also called "by-the-wind sailor" which is likely because they get to sea shores by floating or when they are blown by the wind in large numbers.

Rich Mooi, from the California Academy of Sciences, said that while some believe that these creatures are a type of jellyfish, they are actually distantly related and are only similar superficially. These invertebrates, which measure between 40 and 80 millimeters in length as adults, are marked by a clear chitinous semicircular sail that sticks above the water and can be found floating in the surface of the sea.

Hoards of these animals, which feed on fish and zooplankton and are in turn eaten by snails, are seen in large numbers along beaches in California. Jim Watanabe, from the Hopkins Marine Station of the Stanford University said that it has been years since a similar event has occurred.

"We saw probably this population about 40 to 50 kilometers offshore and they just covered the sea surface," Curtis Roegner, a research fishery scientist at NOAA Fisheries told Washington's KING5. "There were millions and millions of them as far as we could see. It was quite impressive."

Watanabe said that while the mass beachings of these strange-looking creatures are difficult to predict, the wind patterns this year may have been responsible for the presence of the creatures ashore. Watanabe, however, said that velellas need to be back on the water as they cannot survive on the shores for long. The animals do not have the ability to retain water so they could get dried up within one to two hours.

"They're a nice reminder of the diversity of other life in the sea that we sometimes don't think about," Watanabe said. "This is an opportunity to appreciate them and that diversity and to keep it going."

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