(CNN) -- One woman is under water and without oxygen for 30 minutes after a kayaking accident. Another has end-stage cancer. A teenage boy suffers heart failure.
On the brink of death, all three tell stories of leaving their bodies, going to heaven and coming back.
For each, their story raises questions: Is heaven real? What does it feel like to die?
And for each, their answer -- airing Sunday on CNN's "To Heaven and Back" -- will be grounded in their experience. These are their accounts:
It was January 14, 1999, and Mary Neal, an orthopedic surgeon from Jackson Hole, Wyoming, had surprised her husband, Bill, with a week-long kayaking trip with friends in the Los Rios Region of Chile.
It had been a good trip. The couple spent the week enjoying people, the food and the culture.
But that morning, Neal's husband wasn't feeling well. So he stayed behind while she joined their friends on a section of river well known for its waterfalls and drops of 10 to 15 feet.
"When I first put (afloat) on the river, I didn't feel quite right," she said.
Neal crested at the top of the first big drop in the river. She looked down into what she later described as a bottomless pit.
Then she went over.
The front end of her boat got pinned in the rocks, submerging her in the water. The force of the current pinned her to the front deck of the boat.
Her friends began searching for her, knowing that the clock was ticking.
"Time is very important," Neal said. It determines "whether you are going to rescue somebody or recover the body."
Precious minutes ticked by. "I knew I was going to die," she said.
Neal had always worked -- worked to become a doctor, worked at her marriage of 26 years, worked at raising her four children.
But she admits she made very little time for her spiritual life.
"I did take my children to Sunday school, and I tried to incorporate spirituality into my daily life -- and then I would run out of time," she said.
Pinned in the boat and out of air, Neal started to give up.
"I really gave it all over to God, and I really said, 'Your will be done,'" she said.
At the same time, she remembers her brain doing a self-assessment exam. "I could still feel the boat. I could feel the current," she said.
On the surface above her, her friends were scrambling to try to free her.
It seemed hopeless, her friends would later say.
Then something shifted, and another rock was exposed. It was just enough for the group to shift the boat to free Neal, who was sucked out of the bottom of the boat by the current -- with her legs bending back over her knees.
"I could feel the bones breaking. I could feel the ligaments and the tissue tearing. I felt my spirit peeling away from my body, sort of like peeling two pieces of tape," Neal recounted.
As one of her friends grabbed her wrist to try to pull her out of the water, Neal realized she was outside her body watching the rescue effort.
"I could see them pull my body to the shore. I could see them start CPR," she said. "I had no pulse, and I wasn't breathing. One fellow was yelling at me to come back. ...My body was purple and bloated. My pupils were fixed and dilated."
She watched people work on her, but she felt none of it.
"When I saw my body, I actually thought 'Well, I guess I am dead. I guess I really did die,'" Neal said.
As she watched, she said she was met by "these people or these spirits" who started to guide her toward a brightly lit path toward what appeared to be a domed structure.
"It was exploding, not just with light and brilliance and color but with love," she said.
There, she spoke with the spirits. They told her it was not her time to die, that she still had a job to finish, Neal said.
One of the reasons she had to return, they told her, was because of her son Willie.
"I knew very specifically with regard to my son that he was going to die," Neal said. "We talked about how he already fulfilled his job. He'd really already done what he was meant to do."
Then she was back in her body, breathing again. Those involved estimate that Neal had been without oxygen for 30 minutes.
Her recovery would take months, but she no longer took time for granted. It is a journey she chronicled in her book "To Heaven and Back."
Each day took on a new meaning for Neal, who awoke every day wondering if it would be her son Willie's last day.
On June 21, 2009, 19-year-old Willie went out to roller ski with a friend.
He and the friend stopped on a road, near a ridge.
"Wouldn't this be an incredible last sight, if we could never see anything else," Willie told the friend.
Less than a minute later, he was hit by a car and killed.
"I am my own greatest skeptic," Neal said. "I am quite sure that I would not believe my life story had I not personally lived each and every day of it. I absolutely believe that every person can look at their life and see the hand of God."
Most miracles, Neal says, are quiet.
It's that person who calls you when you most need it, she said. It's that person who directs you to someone who changes your life.
On February 2, 2006, Anita Moorjani was in a coma. With her body riddled with cancer, doctors told her husband that her organs were shutting down and she likely would not make it beyond the next 36 hours.
"I was just so tired of fighting to try to stay alive," she said.
Moorjani knew what cancer could do to the body. She had seen it ravage her best friend, Soni, eventually killing her.
So when she was diagnosed with non-Hodgkin's lymphoma in 2002, she was afraid.
In a way, Moorjani had always been afraid -- of living and of dying.
Growing up in Hong Kong, she said she was bullied because of her Indian heritage. She went so far as to lighten her hair and bleach her skin to fit in at the British school she attended.
"I felt I had to apologize for being me," she said.
Then she was diagnosed with cancer, one of her biggest fears after seeing it take the life of Soni.
Slowly the cancer took its toll on Moorjani.
By February 1, 2006, sick and weak, she thought to herself: "Even death can't be worse than this."
So she said she let go.
The next morning, she didn't wake up. Her husband rushed her to the hospital, where the family was told the bad news: Moorjani was in a coma and not expected to wake again.
Moorjani can't put her finger on the exact minute that she says she left her body.
She saw her husband standing next to her hospital bed.
"He was very distraught. He was there by my bedside. I could feel he was willing me to come back," she said.
Moorjani could also hear conversations that took place between her husband and her doctors, far from her hospital room.
She heard them, she said, discuss her pending death. "Your wife's heart might be beating, but she's not really in there," a doctor told her husband -- a conversation, she said, he would later confirm to her after she asked.
Hovering between life and death, she said she was surrounded by people who loved her.
Her best friend, Soni, was there. So was her father, who had died years earlier from heart failure.
There were others there, too. She didn't recognize most of them. But she knew they loved her and cared for her.
It was a feeling unlike anything she says she had ever felt.
"At first, I did not want to come back. Why would I want to come back into this sick body?" she said.
Then, hovering between life and death, she had a moment of clarity -- a true understanding.
"All the years of beating myself up, of feeling flawed, had manifested itself and turned into cancer," she said.
About 30 hours after being hospitalized, Moorjani awoke.
Within days, she said, her organs began to function again. Within weeks, doctors could find no evidence of cancer in her body, she said.
"I'm not scared of death. Whenever that day comes, I'll feel I will have accomplished what I came here to do," Moorjani said. "I believe that all of us have only come here to realize who we are, and to be true to who we are."
She recounted her experience in her book, "Dying to Be Me: My Journey From Cancer, To Near Death, To True Healing."
Today, she remains cancer free.
It was December 18, 2011, a week before Christmas, and 18-year-old Benjamin Breedlove went to his bedroom.
He had spent the day with his family. They had held church at their home in Austin, Texas, because the teenager was ill. Since childhood he had battled hypertrophic cardiomyopathy (HCM), a heart condition that posed a constant risk of sudden death.
In his short life, Benjamin -- Ben as he was known to family and friends -- had suffered three heart attacks, including an episode the night before.
Two weeks earlier he suffered heart failure while he was in school.
He collapsed on the campus commons, according to students and the school nurse.
For three minutes, his heart stopped.
Now, after two heart attacks in as many weeks, he and his family were holding church inside their house. The family read from the Bible and prayed for Ben.
"After we were finished, Ben prayed for us. He prayed that we wouldn't be sad or scared," his sister, Ally Breedlove said.
Then, on that day a week before Christmas, the teenager disappeared into his room where he made a two-part video titled "This Is My Life" that he posted to YouTube unbeknownst to his parents.
He used index cards to recount his collapse at the high school.
"I heard them say 'he's not breathing. His heart stopped, and he has no pulse,'" the cards read.
He said he saw a white light.
The teenager said he felt at peace. "I didn't want to leave that place," he said in his video.
Then Ben said he woke up on the floor of the school.
A week later, on Christmas Day, Ben opened presents with his family. They played a game of Monopoly. Then he went outside to watch his younger brother bounce on a trampoline.
"I looked outside my kitchen window, and I took a mental snapshot of Ben smiling," his mother, Deanne Breedlove, said. "That was the last time I saw Ben smile."
Minutes later, he suffered heart failure.
As Ben lay dying, the video he made had gone viral with hundreds of thousands watching it.
It's closing lines: "Do you believe in angels or God? I do."
CNN's Jennifer Hyde, Tina Matherson and Courtney Yager contributed to this report.
Watch Anderson Cooper 360° weeknights 8pm ET. For the latest from AC360° click here.