Take a look at the photo. We’re both smiling, and our mouths are actually open. Neither Jeb nor I am choking on the water! We can all have water in our mouths, and without even thinking about it, not allow it to enter the throat/pharynx. So when your child has his/her mouth open above or underwater, it’s simply a sign that he or she is relaxed, and instinctively, he/she will likely not choke on or swallow the water.
What if you or a child does swallow a little water? Is he/she at risk of drowning? Of course not! It’s no different than taking a drink. As the water enters the throat/pharynx, the epiglottis closes and prevents the water from entering the respiratory pathways and the lungs, and it enters the stomach instead. Experts do agree that you should avoid swallowing pool water. Chlorine does kill waterborne germs, but chlorine levels fluctuate in pools, especially busy, crowded pools. Germs are not equally susceptible to chlorine, some germs take longer to destroy than others.
If your child or student has their mouth open, he is simply at ease and very relaxed. He is not going to consciously breathe the water into the throat, which may cause him to cough. This usually occurs because a little panic sets, but usually the younger the child, the less common this occurs. The older the child, or the more aware the child is of what is going on, the more common it is for a child to panic and cough a little on the water. This is why by age three, Swim Lessons University Swim Instructor Training teaches instructors to make sure children are choosing to go underwater at their own will, and to never force an involuntary submersion on a child. They will go under happily when they are ready!
When a swimmer coughs or chokes on a bit of water, while it may be a little scary, it is not dangerous. If you ever see a swim instructor laugh it off instead of coddling and bringing more attention to it, the swim teacher is not being insensitive. The swim instructor is redirecting the student’s attention vs. bringing more unnecessary attention to it. This is also the reason why parents and teachers shouldn’t point out to a child that his mouth is open and instruct him to close it as if he is in serious danger. Why scare him and make him nervous over something that’s not worth being nervous over? You would be literally un-teaching what you want to teach.