Ukrainian nurse Viktoria Obidina spent over five months in Russian captivity, forced to drink dirty water, endure beatings and starvation.

But not knowing the fate of her four-year-old daughter tormented her the most.

“They brought us water from a lake, sometimes there were tiny fish in it,” recalls Obidina, who was returned to Ukraine earlier this month as part of a prisoner swap with Russia. “In August, when the (lake) began to bloom, the water tasted of seaweed.”

In an interview with AFP on Monday, Obidina, 26, opened up about her ordeal at the notorious Russian-controlled prison in the eastern Ukraine city of Olenivka.

When Russia invaded its neighbor on February 24, Obidina, an army nurse in the southern port city of Mariupol, was dispatched to Azovstal, the city’s massive steelworks, where hundreds of Ukrainian soldiers crouched underground in a network of Soviet-era tunnels.

Obidina’s four-year-old daughter, Alisa, had lived in the family home with a nanny.

But when food supplies in the besieged city ran out and the Russian bombardment became relentless, Obidina made the difficult decision to take her daughter with her to Azovstal.

“I understood very well: if not us, then who will take care of the wounded?”

In the underground bunker, the four-year-old helped her mother treat injured patients.

“She was such a good athlete, she was so mature! She knew very well that she couldn’t distract me,” Obidina recalled. “She helped me, she gave out medicine. I told her what and who, and she helped me.”

But there were also moments of desperation for Alisa.

“She asked me, ‘Mom, is this our last day?’

“Of course I told her, no, we will live, everything will be fine. But the shelling was massive.

In one of those moments, a soldier in Azovstal recorded a short video with Alisa, in which the ponytailed girl, hiding in the dark bunker with a book in her hand, begs to go home.

The video went viral and helped build international pressure on Russia to evacuate those who remained in Azovstal after the city fell to Moscow. But it also proved fateful for Obidina.

In May, Obidina and her daughter left the plant along with a group of Ukrainian civilians under a hard-fought evacuation deal led by the United Nations.

But Russian forces recognized the mother and daughter from the online video, and Obidina was arrested. Before being transported, she managed to hand Alisa over to another evacuee.

“I was told that the child will be sent to an orphanage and I will be captured.”

Obidina said investigators beat her to force her to reveal information about the Ukrainian army.

In Olenivka prison, she was held in a six-person cell with about two dozen inmates.

During all this time, Obidina had no news of her daughter and no idea what to expect.

Earlier this month, Obidina was transferred to the Russian city of Taganrog, along with other female inmates, where she thought it would be a different prison. The detainees were handcuffed, blindfolded and put on a plane.

Eventually, they were taken by bus to Ukrainian-controlled territory, and Obidina realized a prisoner exchange was underway.

She also learned that her daughter was safe.

With the help of distant relatives and volunteers, Alisa, who turned five earlier this month, has been reunited with her grandmother in Poland.

Obidina says she lost 10 kilos in captivity and is now undergoing psychological rehabilitation at a clinic in Dnipro. She plans to leave the army and devote herself to her daughter.

In Poland, Alisa goes to kindergarten and learns Polish, and mother and daughter were able to talk to each other over the phone.

“She’s grown up so much,” Obidina said.

“She said she misses me very much and is waiting to see me.”