NARRAGANSETT, R.I. (WPRI) — Lifeguards rushed to get everyone out of the water Tuesday after a possible shark sighting at the Narragansett coast.

But – the fin that was spotted about 150 yards offshore belonged to an ocean sunfish, according to the Wakefield-based Atlantic Shark Institute.

Executive Director Jon Dodd tells 12 News it was confirmed by some boaters in the area.

“[The boaters] happened to pull up on it and get a good look at it, literally close up,” Dodd said. “They say, ‘hey, guess what? We’re on top of it, we can see it and we know what it is. No need to worry.'”

The ocean sunfish, or mola mola, is one of the biggest fish in the world and its dorsal fin can cause it to be confused with a shark.

“If you look at them straight on or from the back, you’ll actually see that the fin has some flexibility, it almost flaps a little bit,” Dodd explained. “But if you are looking at it from the side, you don’t see that.”

Mike Healey, a spokesperson for the Rhode Island Department of Environmental Management (DEM), said the fin-sighting protocol was enacted out of an abundance of caution after a lifeguard reported seeing the fin around 12:30 p.m.

As a result, neighboring Salty Brine and Roger Wheeler state beaches were closed to swimming until about 1:50 p.m.

Brad Whetherbee, a shark researcher from the University of Rhode Island, believes that, despite the fact ocean sunfish are harmless to humans, the lifeguard made the right call.

“There are sharks in the water and it is certainly worth the precaution if you see a fin,” Whetherbee said. “People are going to run into sharks, they are going to see them … but fortunately, for people who go swimming in Rhode Island waters, it’s a relatively rare occurrence.”

“Compared to a lot of places where people go into the ocean, Rhode Islanders are relatively safe,” he continued.

Despite not knowing at the time whether it was a shark or a sunfish, many beachgoers were eager to get back in the water once they were cleared to do so due to the record-breaking heat.