The water was only knee deep, but Frankie Delgado III's parents watched him closely as he splashed in the Texas City Dike on Memorial Day weekend. Based on what they saw, they thought their 4-year-old was safe.

But shortly after the outing, Frankie started vomiting and had diarrhea, his family told Houston's ABC affiliate KTRK.

On June 3, the boy told his father that his shoulders hurt and then laid down for a nap. He jolted awake a few hours later, his father said.

“Out of nowhere, he just woke up,” Frankie Delgado Jr. told the station. “He said ‘ahhh,’ he took his last breath — and I didn't know what to do no more.”

Delgado called 911, and his child was rushed to the hospital.

Helpless, the parents watched as doctors tried — unsuccessfully — to save their son.

“I walked in. I could see him lying there; they were still working on him,” his mother, Tara Delgado, told CBS affiliate KHOU. “I'm screaming, ‘Let me just touch my baby! Maybe he needs his mama's touch.’ ”

Although Frankie's autopsy results are pending, the family told local news outlets that doctors think he was a victim of “dry drowning,” in which a person is killed by liquid trapped in the respiratory system after he or she has left the water.

Doctors found fluid in Frankie's lungs and around his heart, according to KTRK. His parents told Texas media outlets that they were sharing their son's tragic story to prevent other such deaths. The family did not respond to messages from The Washington Post seeking comment.

It's a rare affliction that can strike hours or even days after a child has left the water, doctors say. Everyday, 10 people die from unintentional drowning, according to the Centers for Disease Control and Prevention. Of those, two are 14 or younger. Drowning is the second-leading cause of “injury death” among children ages 1 to 14. The agency does not collect statistics on “dry drowning.”

Doctors have shied away from the terms “dry drowning” and “secondary drowning,” preferring to specify the circumstances of someone's death to improve resuscitation treatments. In 2002, the World Congress on Drowning produced a comprehensive definition of drowning and rejected terms such as “wet drowning” and “secondary drowning.” But the terms are still used as an imprecise shorthand to describe atypical drownings.

In dry drowning, a person's larynx closes in an attempt to stop water from seeping into the respiratory system, according to the Cleveland Clinic. But air can't get through, either, depriving the body of oxygen. In secondary drowning, water is trapped in the respiratory system. It causes the lungs to spasm, making it difficult for a person to catch a breath. The lungs can also get irritated and fill with fluid.

Olympic gold medalist Tom Dolan shares rules to ensure children stay safe while in the water. (Whitney Shefte/The Washington Post)

But Michael McHugh, the acting chair of the pediatric critical care unit at the Cleveland Clinic, stressed that doctors have tried to avoid catchall phrases such as “dry drowning” so they can improve treatments for specific circumstances.

A patient's treatment “depends on where in this whole process a rescue may have occurred and an intervention may have taken place,” McHugh told The Washington Post.

He said it was premature to say that Frankie's death was the result of an atypical drowning, noting that symptoms of hypoxia, or a lack of oxygen, usually manifest rapidly.

“If a child or adult had been under long enough and had been starved of oxygen long enough, they wouldn't be acting normal,” he said.

The Harris County coroner said autopsy results are pending. The doctor performing the examination has requested additional lab work.

Meanwhile, Frankie's relatives are preparing to bury the 4-year-old — and warning other parents about ‘dry drowning.’

“There are no words to describe how heartbroken we are over the passing of Baby Frankie,” a family member said in a GoFundMe page set up to help cover expenses for the funeral, which is planned for Saturday.

Earlier this week, rocking back and forth in front of a television news camera while a relative recorded the interview for Facebook Live, Frankie's mother shared memories about her son's love of baseball.

“He came home from school and grabbed his uniform, even though baseball season was over,” she said. “He said, ‘Come on mommy, let's go play baseball.’ That's what he wanted. Baseball. Everything baseball. He touched so many hearts, so many people. If you didn't know him by the time you left, he was going to touch you.”

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