It is called dry drowning, or secondary drowning. When children who seem to be fine after being rescued from drowning get into serious trouble hours later. Fortunately, experts say, it’s also very rare.
The child isn’t actually drowning, it’s a late delayed pneumonia in response to water getting into the lungs. You can get a the same reaction from aspirating a tiny piece of peanut.
A few teaspoons of water going down the wrong tube can the result in the lungs becoming irritated and inflamed and then start to produce fluid.
If a child chokes or sputters after going under water but seems fine and hours late starts breathing faster and is finding it harder to breathe and starts coughing a lot, then you want to should take him to the hospital.
Ultimately the best prevention is to make sure your kids know how to swim, and to make sure that an adult is present wherever children are swimming.