Old Lyme ― A 56-year-old woman from South Hadley, Mass., on Sunday became the first known person to swim the entire 410-mile length of the Connecticut River.

Kari Kastango, a lifelong swimmer and board of trustees member for the nonprofit group Connecticut River Conservancy, climbed out of the water Sunday onto Old Lyme’s Great Island Boat Launch. She was met with adulation from a crowd of about 50 people, which consisted of family, friends, spectators and fellow nonprofit members.

Kastango would later say how shocked she was to see how many people had come out to watch her complete her four-year mission.

“I was in awe just to see so many people at this boat launch and cheering me on. Just ― truly touched,” Kastango said.

Each of those four years, between Memorial Day and Labor Day, Kastango had swam the river in small sections, starting in New Hampshire and working her way downstream to Long Island Sound in Connecticut.

As she swam the final leg, about 20 people watched her from a boardwalk beside the river, waving signs that said “We heart the river” or “Team Kari + The River.”

“It was enjoyable,” Kastango said after drying off and changing into a sweater. “I mean it’s always enjoyable ― even when my face is cold and I stop and drink some hot water with honey in it and then I have to start up again and it takes another 10 minutes for my face to sort of get numb.”

Kastango said Sunday’s water temperature, which was in the low 60s, was not as bad as the northern portions of the river she has swam. In this section, she said she had hit some “warm spots” as well as “some jellyfish.”

Kastango had completed 83 swims since beginning her journey from the northernmost portion of the river. She closed it out Sunday with a 2.6-mile section from the Department of Energy and Environmental Protection’s Marine Headquarters to the boat launch.

“It was never about a specific goal,” Kastango said. “It was just take it one day at a time. I was committed to finishing this and there was (many other) people committed to me finishing this so it would finish when it finished.”

Each time she completed a new section, Kastango’s wife, Alison Garvey, friend Julie Paradis, or fellow Board of Trustees member Tim Lewis had trailed her in a canoe, motorboat or kayak and made sure she stayed on her course and closely watched for hazards.

Lewis said Kastango’s prowess as a swimmer made his job as a lookout very easy.

“When Kari is swimming, she is completely aware of her surroundings,” he said.

Sometimes while Kastango swam, Lewis said she would spot an animal or a natural landmark that had a “special meaning” to her and ask him to take a picture of it for her.

Kastango, who has a great fondness for the river’s natural beauty, hopes to make people more aware of the significance of the river, as well as the past and future efforts to reverse its historic pollution problems.

“Us being alive is a gift,” Kastango said. “And having the Connecticut River and the tremendous diversity of wildlife is a gift. And all of us here are tremendously fortunate.”

The Connecticut River Conservancy presented Kastango with a medal and a certificate acknowledging her historic feat.

d.drainville@theday.com