(KTLA) — Bizarre sea creatures that resemble jellyfish have returned to Southern California waters a year after millions were spotted between Ventura and San Diego counties and beyond.

Velella velella, more commonly known as by-the-wind sailors, are oval-shaped blobs that live on the ocean’s surface, propelled by small, stiff sails that catch wind and take them across the globe. Ocean currents and winds move the creatures from place to place, allowing them to catch their prey with their stinging tentacles.

Always lurking, but not always in the area, the Vellela vellela are often pushed toward the California coast by powerful spring storms.

Last year, Californians visited local beaches in droves to catch a glimpse of the creatures both on the beach and atop the waves. In 2014 and 2015, trillions of them washed up along the eastern Pacific coast, according to Cassandra Davis at the Aquarium of the Pacific in Long Beach. 

By-the-wind sailors are a type of hydrozoa that feed primarily on plankton and closely resemble the Portuguese man o’ war, a venomous sea creature that’s a known nuisance for surfers throughout the Pacific Ocean. Unlike the man o’ war, Vellela vellela stings are considered to be mild to humans.

While their stings might not bring you to your knees, swimmers, surfers and other water recreationists are urged to avoid going into a crowd of by-the-wind sailors.

Meanwhile, another sea creature is more than happy to have the floating blobs in the area. Mola mola, commonly known as the ocean sunfish, are big fans of Velella and have been spotted in recent days gorging on the ocean-current transients.

They also occasionally get eaten by sea birds and sea turtles, but their venom and lack of meat make them an unappetizing meal for more predators, experts say.

Jessica Rodriguez, of Davey’s Locker Whale Watching in Newport Beach, said they’ve seen hundreds of the by-the-wind sailors in recent days and shared images of an ocean sunfish feasting on them.

The thousands of by-the-wind sailors that have appeared recently in California will either be eaten by predators, pulled back into the ocean by the tide, or die and rot away on the surface.