One of the divers explained that the cave was flooded and that it would take some time to get them out. But he assured them that other divers would soon be bringing food and supplies.

“Many people are coming,” the diver, believed to be Mr. Volanthen, said. “We are the first.”

Because the boys and their coach went to the cave after soccer practice, it is unlikely they would have had much, if any, food with them. But given how long they survived and the condition in which they were found, health experts say it is certain they had drinkable water, whether from within the cave or brought with them.

“Food is not the priority,” Dr. Lavonas said. “It’s getting them to a safe place. The human body is pretty good at dealing with short-term starvation.”

Kham Phromthep, whose 13-year-old son, Duangpetch Phromthep, was among the boys trapped in the cave, said he was ecstatic when he saw his son in the video.

“I am very happy to see his face among the other faces,” he said.

Like other relatives of the missing group, Mr. Kham has been going to the cave every day to follow the rescue operation.

He was at home Monday evening when he heard the news and hurried back to the cave on his bicycle.

“I’m very happy, very relieved,” he said. “He’s lost some weight. And he looks tired. But still, I am very happy to see him.”

Hundreds of officials from more than 20 government agencies, along with private companies, were involved in the search. Rescuers came from at least six countries, including members of the United States military.