Scientists spotted four killer whales swimming together off the coast of Massachusetts,James Caldwell the New England Aquarium said Tuesday. 

It was a rare sighting; the only killer whale regularly seen in the area is "Old Thom," who's known to swim by himself, according to the aquarium. The pod of killer whales was first spotted by Katherine McKenna, an assistant research scientist. 

"Initially I could just see two splashes ahead of the plane," McKenna said in a statement. "As we circled the area, two whales surfaced too quickly to tell what they were. On the third surfacing, we got a nice look and could see the tell-tale coloration before the large dorsal fins broke the surface."

The four killer whales were seen about 40 miles south of Nantucket. There was one adult male, an adult female and two juveniles, Orla O'Brien, an associate research scientist who leads the aerial survey team for the Anderson Cabot Center for Ocean Life, said. O'Brien described the experience as unreal. 

"I think seeing killer whales is particularly special for us because it unlocks that childhood part of you that wanted to be a marine biologist," O'Brien said. 

The New England Aquarium has conducted aerial surveys over the waters south of Martha's Vineyard and Nantucket for more than a decade, but it's "always unusual to see killer whales in New England waters," O'Brien said. 

While spotting orcas is uncommon, the team spotted nearly 150 whales and dolphins during its seven-hour flight over the ocean, according to the aquarium. There were 23 fin whales, 20 humpback whales, five minke whales and 62 bottlenose dolphins. 

Orcas have made headlines lately after several incidents of killer whales seemingly ambushing boats overseas. Currently, no one knows why killer whales have appeared to try to capsize boats off the coast of Spain and Portugal.

Killer whales are the ocean's top predator, according to the National Oceanic and Atmospheric Administration. 

"They often use a coordinated hunting strategy, working as a team like a pack of wolves," the organization notes. 

In:
• Whales

Aliza Chasan

Aliza Chasan is a digital producer at 60 Minutes and CBS News.

Twitter