- By-the-wind sailors are beginning to wash up onto shores in California.
- Beaches from Dana Point to Point Reyes National Seashore have seen the creatures on their shores.
- The animals aren't dangerous to humans, but they can sting.
Blue jellyfish-like creatures known as by-the-wind sailors are beginning to dot the coastlines of California and are reaching as far south as Orange County.
On Friday, Dana Wharf Whale Watching, which operates off the coast of Dana Point, California, said that they had seen "hundreds" of the sailors in the water, and displayed two on one of their whale watching boats.
"Watch for them on the beaches," Nona Reimer, a science teacher who goes by Nona the Naturalist, said in an Instagram video for Dana Wharf Whale Watching. "They're gonna be washing on the shore pretty soon."
Known by the scientific name Velella velella, the hydrozoa is actually a collection of polyps that float through the ocean using a translucent "sail" that sits upright on a flat, oval body to catch the wind. The creatures are part of the Cnidaria group, which includes jellyfish and corals.
Once the creatures are stranded on the beach, they can disintegrate and die.
The carnivorous, tentacled organisms eat zooplankton and other small sea creatures. Although they resemble the poisonous Portuguese man o' war, the by-the-wind sailors are not poisonous. Their stingers can irritate the skin, however.
"You may come across a fresh wash-up of Velella, tinging the stretch of shoreline blue, but if they've been there a while, they will look like crinkly and dry ovals of cellophane," Point Reyes National Seashore wrote in a Facebook statement.
The sailors often wash up on the shores in the spring and summer, according to the Point Reyes National Coast, when strong winds — like the ones associated with the recent storms across California, push them towards the sand.
There is also some evidence their presence may be a sign of El Niño events, which warm the ocean water in the Pacific Ocean and result in a change in weather patterns across the globe. NOAA estimates that El Niño would form this summer.
In 2014 and 2015, a Velella bloom resulted in billions of by-the-wind sailors washed ashore beaches from California to Washington. Some experts say the massive blooms could become more common as a result of climate change warming the waters in which they live.
Dana Wharf Whale Watching did not immediately respond to Insider's request for comment.