A pair of blue whales, the largest creatures alive on Earth, was spotted researchers from the Blue Ocean Society of Marine Conservation off the coast of Rye Harbor in New Hampshire.

According to Jen Kennedy, executive director of the conservation group, spotting a blue whale in New England is rare, but spotting two of this gigantic mammal together is rarer.

"We might see a blue whale every five to 10 years, so it was possible, but rare. And we've never seen two together in our last 20 years of whale watching and research off the New Hampshire coast," said Kennedy in a report from The Guardian.

The whales were spotted while Kennedy, along with their group's co-founder Dianna Schulte, was working aboard Granite State last Friday. Schulte plans to send pictures of the whales to researchers in Canada to learn more about the two marine mammals.

Blue whales are considered to be the largest animal ever known to have existed. It can grow from 24 to 33 meters long and can weigh up to 200 tons. With only about 10,000 to 25,000 blue whales around the world, most marine biologists consider them to be the most endangered of the great whales.

This kind of whales could live in oceans but not in enclosed seas and the Arctic. In the Atlantic, blue whales are usually spotted off of St. Lawrence in Canada.

According to ths World Wide Fund for Nature, commercial whaling activities in the 20th century almost wiped out the global population of blue whales. The organization believes that in the 20th century alone, a total of 360,000 blue whales have been slaughtered in the Antarctic.

After receiving worldwide protection in 1967, the global population of blue whales is slowly recovering. The blue whale population in North Pacific makes up approximately 2,000 of the species' global population.