What is the Labor Day holiday weekend, the last big beach weekend of the summer, without a good shark scare?

They got one Monday on Wells Beach in Maine. But it turned out that the three gray fins that kept protruding from the water, prompting lifeguards to order swimmers onto the beach, did not belong to sharks, after all.

They were determined to have belonged to ocean sunfish, bizarre-looking but harmless creatures with truncated bodies and tall fins (generic sunfish image at right is courtesy of NOAA; image below was captured off San Diego by Daniel Botelho).

“They are docile. They are no threat to humans,” Dan Moore, Wells Fire Chief, told the Portland Press Herald.

Perhaps nerves were frayed by so many reports of great white sharks–and even one report of a great white attack–just down the coast off Cape Cod, Massachusetts.

One person, after seeing the fins, telephoned 911.

The beach closure spanned 2.4 miles and lasted 30 minutes because of the sighting, and after the species was identified, everybody got a good laugh. “We probably get a couple calls a year, people seeing them off beaches,” said Aimee Hayden-Roderiques. “It could be a shark so they err on the side of caution, but hopefully not on the side of panic.”

Ocean sunfish, also called mola molas, are the world’s largest bony fishes and can weigh more than 2,000 pounds. Their moon-shaped bodies can span eight feet across. They’re alien-like in appearance and sometimes maneuver through currents looking clumsy, or injured.

“It’s very, very awkward when it’s at the surface,” Hayden-Roderiques said. “The fin sticks up, moving side to side because they’re wobbly. It kind of looks like a drunk shark, if you will. Shark fins are pretty stable and moving forward.”

People were asking if it was safe to go back into the water, even after lifeguards gave the green light.

Ocean sunfish have been making news on the West Coast, too, with sightings way above normal off California, explained by an abundance of sea jellies. Earlier this summer Daniel Botelho published a remarkable sunfish image that went viral on the Internet (second image on this post), for reasons that probably do not need to be explained.