A South Carolina 10-year-old died tragically on Sunday an hour after swimming because of “dry drowning,” a little known phenomenon that killed about 3,600 Americans in 2005, according to the latest statistics of the Centers for Disease Control and Prevention.

What exactly is “dry drowning?” Like conventional “wet” drowning, “dry drowning” is a form of asphyxiation. The phenomenon happens when a small amount of water gets into the lungs and damages the tissue, causing the lungs to fill with water. That results in the lungs being unable to deliver oxygen to the blood and, ultimately, the brain.

The warning symptoms of “dry drowning” are extreme drowsiness, breathing problems and dramatic behavior changes. The paradox is that the boy, named Johnny Jackson appeared to have just one of these symptoms, as his mother Cassandra Jackson told NBC News in a story broadcast Thursday on the TODAY show.

On Sunday, she had taken her son to a pool near their home in Goose Creek, S.C. for the first time. At some point, Johnny swallowed some water while swimming and, when they arrived home he complained he was tired. After a bath, he went to sleep.

When checking on him later, his mother found him with his face covered in a “spongy white material.” He was immediately rushed to Trident Hospital but it was too late, as he already died.

“We physically walked home. He walked with me,” Jackson said, still trying to understand how her son could have died. “I bathed him, and he told me that he was sleepy. I walked over to the bed, and his face was literally covered with this spongy white material. And I screamed.”

The tragic death of Johnny should be taken as a warning, as parents or caregivers are rarely aware of the fact that drowning can still kill hours after being submersed in water, Dr. Daniel Rauch, pediatrician at New York University Langone Medical Center told Meredith Vieira on the TODAY show. He urged parents to look for all three signs of dry drowning, but, at the same time, he also expressed his sympathy for Johnny’s family and said it is difficult to spot the symptoms in kids, as they usually change their moods very quickly and get tired after playing or doing activities specific for their age.

However, if a parent notices dry drowning’s symptoms in their child after swimming in a pool previously, they should immediately rush them to a hospital for a check. If there's water in the lung, the doctor puts a tube into it thus forcing oxygen through under pressure. Then the lung heals itself in time.

Unfortunately, for Johnny time and lack of visible symptoms were his worst enemies, which killed him in the end.