Secondary drowning is a rare condition where someone experiences a near-drowning and may appear fine, but sometimes hours later dies as a result of fluid left behind in their lungs.
Doctor Kristen Samaddar with Phoenix Children's hospital said when someone is drowning, they end up inhaling water that goes through the trachea and into the lower airways.
"Which can damage the lungs and cause the body to be lacking the oxygen it needs to function properly," Samaddar said.
If someone is pulled from the water and revived, they can be conscious and alert but the small amount of water left inside their lungs can continue to cause damage and could eventually be fatal.
Samaddar said the condition is so rare that there is varying opinions on exactly what is happening during a potential secondary drowning.
"I think that the exact physiology of what happens with a secondary, or dry drowning, is not known because it is such a rare event," she said.
If someone has had a near-drowning event, Samaddar said to keep and eye on them and don't assume they're OK because secondary drowning can occur long after surviving the near-drowning.
She recommends that if someone was involved in an incident where CPR is necessary, it's very important they see a doctor to make sure there isn't water left in their lungs or serious damage.
"We want to make sure they are returning to normal functioning," she said. "We will be looking at how comfortable they are breathing, depending on the significance of the drowning event that happened to be non-fatal, there may be other organs that are involved."
Tiffaney Isaacson, water safety coordinator for Phoenix Children's Hospital said the best defense against a secondary drowning is to prevent the near-drowning event from ever occurring.
While secondary drownings are extremely rare, Isaacson said drownings are not.
Arizona has one of the highest rates in the country for child drowning and with six drowning involving children and teenagers in May alone, she said it's important to remember some simple safety tips to help save lives.
"We want parents to really focus on two things to prevent an emergency, the first is constant, capable supervision when children have access to the water," she said. "The second is barriers to prevent a child from getting to the pool without good adult supervision, an example of a good barrier is a pool fence."