There's a big white whale swimming off the coast of Seattle, and no one knows why.

Over the past week, people in the greater Seattle area have spotted the white whale swimming around Puget Sound. The wayward cetacean — a beluga — is normally found in Arctic and subarctic waters.

"The closest beluga population is Cook Inlet, Alaska," which is about 1,500 miles (2,400 kilometers) away from Seattle, Howard Garrett, co-founder of Orca Network, a nonprofit that raises awareness about whales in Puget Sound, told Live Science. "I haven't checked the water temperatures there, but I'm sure they're a bit colder up there than here."

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One of the first reported sightings occurred on Sunday (Oct. 3), when Jason Rogers, of Bonney Lake, Washington, filmed the white whale swimming in Commencement Bay near Tacoma, about 30 miles (50 km) south of Seattle.

"It was a surreal experience, to be sure," Rogers told Live Science in an email. "Sailing in Commencement Bay was the last place we thought we would see a whale, much less a beluga! There it was, swimming along peacefully, although it really felt out of place."

Other people spotted the beluga (Delphinapterus leucas) around Puget Sound, even swimming by three different shipyards. "I don't understand the attraction of a shipyard to a beluga," Garrett said. "I don't know if that's a clue, if that means it had been held captive at a shipyard somewhere at a busy port, but we have no documents, no idea of where that would be, certainly in North America."

In 2019, a beluga whale wearing a harness that read "Equipment of St. Petersburg" and spotted in Norwegian waters was suspected of being a Russian spy, Live Science previously reported. That beluga, nicknamed Hvaldimir, is still swimming in Scandinavian waters; animal welfare activists are worried it may not be able to hunt by itself and avoid humans, according to the BBC.

There aren't any clues hinting at the newfound beluga's origins. "We've seen no markings, no indication of where it comes from," Garrett said.

Like many other Arctic and subarctic animals, beluga adults are white, which helps them stay camouflaged in a world of snow and sea ice, according to the Georgia Aquarium. Belugas are also known for their unique "melons," the round bumps on their heads that the whales use for communication and echolocation. In fact, belugas are social animals that live in pods of as many as 100 individuals, Garrett said, which makes this lone whale's journey all the more mysterious.

So, why did this whale venture out on its own?

"Until we have some indication, my default theory is that this whale just decided to go out walking, go explore," Garrett said. "It wanted to travel. It's highly unusual, but every now and then it happens with different [beluga] populations. So, it's not totally unprecedented, but definitely very rare."

The last documented sighting of a beluga whale in Puget Sound was in 1940, Garrett said. There was also a report of a beluga in Puget Sound in 2010, but only one person reported seeing it, and they weren't able to get any photographic evidence of it, he noted.

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In 2020, a beluga whale washed up dead in Baja California Sur, Mexico, according to The Mercury News. It's still a mystery why that whale swam to such warm waters. "I don't know why a beluga would do that," Garrett said.

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That said, the Puget Sound beluga appears to be in good health, at least according to sightings of it so far. Belugas eat squid, small fish and crabs, "and there's plenty of that in Puget Sound," he said. Puget Sound is also home to other whales, including transient and resident orcas and migrating gray whales, humpback whales and minke whales, Garret said.

Local whale and other animal groups are aware of the wayward beluga, including the local branch of the National Oceanic and Atmospheric Administration (NOAA), which hopes to safely approach the whale to get images of it. Such images could be compared with photos of other known beluga whales, and might help scientists identify where the Puget Sound visitor came from, Garrett said.

To report a sighting of the beluga, call the Whale Sighting Network at (360) 331-3543 or toll-free at (866) ORCANET (672-2638); or you can email [email protected]. But don't get too close to the cetacean; they're protected by the Marine Mammal Protection Act, which requires that watercraft stay at least 100 yards (91 meters) away, although a greater distance is recommended, according to Whale Wise.

Originally published on Live Science.