He was last seen struggling against the current, terribly emaciated, one of the skinniest orcas ever seen alive.
The dorsal fin that once towered from his trademark starburst saddle patch was completely collapsed across his back. He had lost so much body fat, he could barely keep his body afloat.
K21 is presumed dead since that terrible sighting on July 29.
With his passing, there are only 74 endangered southern resident killer whales left in the population.
The grief felt by many right now is not only for a beloved whale, but for the passing of a way of life in the San Juan Islands, where the southern residents hardly visit any more. And when they do, they are too often struck by tragedy, carrying their dead calf or breathing their last breaths.
And K21 was the oldest male in the southern residents — at only 35. That also raises the troubling specter of the shifting baseline of age for these animals.
"I don't want to just write these guys off at, 'Oh, 35, that is the end of their lifetime,'" said Deborah Giles, an orca specialist at the University of Washington's Center for Conservation Biology and science and research director for the nonprofit Wild Orca. "We can't let dying at 35 be considered the new normal, or a natural end at the end of a long life," Giles said. "This death was neither."
"We know they have the capacity to live past 35 and there is nothing that biologically limits them to that. We know from past whales that they live to be older, and to be bigger."
No one knows why K21 died, and if his body is not recovered he takes that mystery with him.
But this much is for certain: at 35, he died at what is considered an average age, but still died younger and smaller than males before him.
Other males, J1 and L41 — the mighty Mega — lived longer and fathered between them 13 calves after their 35th birthday, Giles noted. J1's last known calf was born the year he died, at age 59.
"These older males show it is not only possible to live much longer but older males also are more likely to father calves," Giles said.
Researchers have documented in a 2008 paper that male orcas in the Gulf of Alaska commonly lived into their 40s and 50s.
The last decade has seen a loss of prime breeding-age whales as well as high mortality in calves under 5 years of age. Those losses — put together with a high rate of failure in southern resident pregnancies — bodes ill for the southern residents. K pod has not seen a successful live birth in 10 years.
K21 was not known to have sired any calves. Could it be his reproductive capacity was suppressed by pollution? We will never know.
The average life span accepted for male southern resident orcas today is based on 42 years of data during what are likely the leanest fishing years the southern residents have ever experienced. The southern residents coevolved with the Chinook they preferentially feed on in the northeastern Pacific thousands of years ago.
The southern residents have lost 15 family members in five years — six of which showed signs of not getting enough to eat, including loss of so much body fat their head became misshapen, a condition that often precedes death.
The majority of southern resident pregnancies are lost, and the cause is tied to nutritional stress, research shows.
Unknown is what the southern residents' life span was like before industrial fishing, dams and development transformed the environment in which the whales must subsist — and depleted Chinook runs, which are in trouble virtually everywhere the southern residents hunt.
K21 disappeared in waterways that traditionally were the most important summer feeding ground for the southern residents. But this summer the whales have barely been seen in the San Juan Island waters at all, instead searching elsewhere for food.
"This whales' absence from their historic foraging areas is a signal that the ecosystem is out of balance, unable to support predators at the top of the food chain," Giles said. "This should be a loud warning bell and not just an acceptance that these whales now feed elsewhere."
Lack of Chinook salmon is one of the main threats to the survival of the southern residents, in addition to noise and disturbance from boats that make it harder for the whales to hunt, along with pollution.
"The take home is we have to increase the amount of Chinook salmon available to them," Giles said.
Kelley Balcomb-Bartok grew up on San Juan Island and said he has known K21 all his life.
"He was a very exuberant and fun whale, there was an energy to him and a joy."
K21 stands for something so many miss, Balcomb-Bartok said, when the southern residents were just part of every summer day.
"It's a lost era, a lost place, those long summer days even before the sun rose you could hear the blows of them resting and relaxing, their tummies are full, they are just enjoying life. There was a joyfulness to the time and the place and the animals. That is what everyone pines to return to."
He was filled with dread when he first heard about an orca seen struggling last month. Then he saw the gruesome photos of what he thinks must be K21's last days.
It doesn't feel right to see the population without male elders, Balcomb-Bartok said.
"He was the oldest male," he said of K21. "And that is not saying much any more."