Their friendship had just started.

Herman Tsakhaev, 9, of Sudbury, and Bodie Thompson, 11, of Lincoln, were kayaking and paddle boarding on Walden Pond Sunday when they saw an adult struggling in the water.

“He was drowning, I think,’’ Tsakhaev said in a phone interview. The two youngsters, who met an hour before the incident, hoisted the man onto Tsakhaev’s yellow kayak and paddled him to shore from the middle of the pond, Tsakhaev said.

Tsakhaev said he thinks the man must have had a stiff leg.

“It happens often,’’ he said. “His leg looked very pale.’’

Sehnaz Thompson, Bodie’s mother, said she was confused at first as she watched her son make his way to the part of the pond she had asked him not to go to, because it was out of her sight.

Little did she know he was trying to save a swimmer in trouble.

“I started kind of, like, panicking,’’ she said in a phone call Sunday night.

As the two boys saw the man who was waving his arms and calling for help, Bodie was a bit uneasy, too, he said.

“I didn’t know if he was going to drag me to the woods or something,’’ he said. “But I felt it was right.’’

To add to the confusion, people started congratulating her son and his new friend when they made it to shore.

“I was like, you just saved someone’s life — that’s incredible,’’ Thompson said.

Bill Noke, Concord Fire Department shift captain, said he saw the boys upon arrival, after receiving a call about a distressed swimmer on the Lincoln side of the pond. The swimmer, who has not been identified, suffered a light cramp, he said.

“When we go down there, it’s not always a great outcome,’’ he said. “It’s always nice when we have an outcome like this.’’

In a tweet Sunday, the Concord Fire Department account lauded the two boys for helping the man until officials arrived to the scene.

“It’s a great story — I mean, they saved a guy,’’ Noke said.

For Tsakhaev, who said he is a second-grader at General John Nixon Elementary School, it was just what he and his new friend had to do — be responsible.

“Any person who would have ended up in the same situation’’ would have done it, he said.

Alejandro Serrano can be reached at alejandro.serrano@globe.com.