There were no stores on the island. Fearful of arrest by the Russians, Ms. Krupych, 40, did not dare venture deeper into Russian territory.

Instead she called acquaintances and asked to borrow from the pantries of their empty summer homes, and she fished. She and her children, Maksym, 12 and Maria, 4, also hunted for canned goods in the ruins of homes destroyed by shelling.

“That’s how we survived,” she said. “There was no possibility to buy food or go anywhere.”

Maria was too young to understand the predicament, she said, but Maksym became worried and took to biting his nails. “The child was stressed,” she said.

After the dam breach, the family piled into a boat to get to safety in the upper story of a neighbor’s three-story home. While climbing in a window, the roiling water carried away the boat with her father and a neighbor still aboard.

“I desperately screamed, ‘Do something!’” Ms. Krupych said, but the current washed the boat out of view. “They tried but the water took them away into the night.”