Warning: video contains graphic language.
It was a slow day of tuna fishing for a group of friends bobbing in a boat 12 miles off the coast of Chatham this week. But then they witnessed a rare event: an apparent pod of killer whales swimming close by.
Alex Wyckoff, 17, of Brewster, said he was on the "Fish Box," which launched from Nauset Marine East, in Orleans on Tuesday, when he and three friends spotted a flock of birds hovering over the ocean's surface.
Because they hadn't had much luck fishing, Wyckoff, who was with Matt and Mark Ward, 21 and 18, respectively, and Justin Daly, 20, said the group steered toward the commotion. The birds were above spouts coming from the water, which they believed were from humpback whales.
Suddenly, the friends realized these were different creatures.
"We did not know they were orcas at first, because we only saw the spouts," said Wyckoff. "Matt and I ran and got up onto the tower as quickly as possible, while Mark and Justin stayed below. We were at first in disbelief."
Wyckoff said as they continued to head north, the orcas began swimming around their boat. One whale breached about 40-feet from the bow, he said. At another point, two of the ocean predators came right up alongside the "Fish Box."
"We have seen white sharks, but since the whales are foreign to these waters for the most part, we were ecstatic," he told the Globe in an e-mail. "They ended up being very playful ... Really an amazing experience!"
Wyckoff and his friends shared video that they took of the whale encounter with the Atlantic White Shark Conservancy this week. The non-profit posted the video to their Facebook page, and shared it on Twitter and Instagram. They called the footage "incredible."
Officials from the New England Aquarium confirmed that what Wyckoff and his friends had witnessed were killer whales.
Philip Hamilton, a research scientist at the Anderson Cabot Center for Ocean Life at the Aquarium, said, based on his review of the video, the group saw at least two or more whales, all of them female.
Hamilton said he couldn't estimate how big the animals were. But female killer whales, like the ones seen in the video, can grow up to 23 feet in length, and weigh four tons, according to Aquarium officials. Adult males, experts said, can reach 30 feet, and weigh up to eight tons.
The only other orca sighting Aquarium staff are aware of this summer locally came in July, when a commercial fisherman took a photo of a 6-foot slick black dorsal fin 13 miles northeast of Chatham. That orca, which was alone, was later identified as "Old Thom," a 30-foot-long whale known to researchers.
Seeing a group of killer whales so close to the coast, officials said, is a different story.
"It's a lucky and rare sighting to be able to see one, let alone a couple," Hamilton said. "Their enthusiasm was warranted."
The excitement is obvious in the video captured by Wyckoff and his friends, and shared online. As they watched in amazement, a passenger can be heard shouting, "It's a killer whale, baby!"
Tuna? What tuna?