Thousands of mysterious, bright blue sea creatures washing up along California beaches have made their way to San Diego.

The sapphire-hued Velella velella, which look like tiny jellyfish, are floating ashore in Del Mar around 15th Street, just south of Power House Park.

Measuring about three inches, the invertebrates are known as “by-the-wind sailors” because part of their body resembles a sail sticking above the water.

Wind and ocean currents are bringing the Velella velella to our coast, Jenn Moffat with Birch Aquarium told NBC 7.

While they are related to jellyfish, their sting typically cannot be felt, so they’re harmless to humans.

Still, Moffat has a word of advice.

“Don't touch them unless you know for sure this is what you're dealing with,” She said. “They look very similar to Portuguese man-o'-war, and those have a pretty powerful punch as far as sting goes. So it's just really better to stay away from them and just look at them and let them be.”

Moffat said once the Velella velella make it to shore, they are dead or dying.

Nevertheless, their eye-catching color has raised the curiosity of beachgoers.

“I had no idea what it was,” said Tom McKissick. “I understand it's from the jellyfish family or something but it doesn't sting. So, it's a friendly jelly fish.”

Northern California was the first to see the sea creatures rolling in by the hundreds last month. Researchers say they feed on zooplankton and fish, and their natural predators are snails.