HOLLYWOOD, Fla. -

Nothing is more refreshing  on a hot summer day, then playing in a pool, and swim lessons are absolutely essential.  But even a child out of the water can be in danger of drowning. Doctors call it secondary or dry drowning.

"If you  go into the pool and water goes into your lungs, your lung reacts to that water, it swells up and then over time, you have difficulty breathing, low oxygenation, a child looks very tired," explained Dr. Peter Antevy with Joe DiMaggio Children's Hospital in South Florida.

Symptoms can take 1 to 24 hours to show up. That's what happened to 2-year-old Brooke Adler. She was fine all day after her first swim lesson, but she woke up that night with what sounded like an asthma attack.

"She couldn't stop coughing. It was uncontrollable, asking for water she was pointing in her mouth, 'It hurts, it hurts," explained Brooke's mom, Leanna Adler.

Antevy says he has seen a number of secondary drowning cases.  He says even swallowing too much water can cause that dangerous, even deadly, chemical imbalance, which is why parents need to know the warning signs.

"You have to look for signs of lethargy, not acting right, that's probably the most important sign. Difficulty breathing, so having a difficult respiration," explained Antevy.

Brooke's mom read about dry drowning and was understandably concerned.

"We were  both thinking, 'Well maybe she's fine, and are we over-reacting?' But I'm glad that we followed our instincts," she said.

In the emergency room, Brooke was given oxygen and medication for the swelling in her lungs and now  the toddler is happy and healthy.