This is a very rare complication after getting a mouthful of water which makes you cough violently.
The natural reaction of the body is to close off the airway to prevent water getting in to the lungs. Water usually goes in to the stomach rather than the lungs.
Getting a mouthful of water and coughing to expel the water from the back of your throat is common in both Adults and Children.
Though rare, we do need to know what to do if there is any complication..

if an adult or child spluttered and coughed for an extended period of time while swimming, but then an hour or two hours later starts having progressively worse bouts of coughing, seemingly out of nowhere, then this is a concern.

Shortness of breath – another sign would be shortness of breath. If your child is breathing faster than normal, and not just for a few seconds, but sustained over several minutes, then this may be a cause for concern.

Behavior change – Here, your child might be confused, might speak more slowly than normal, or might do things that don’t quite fit with their usual behaviour. Something that wasn’t normal for your child, this may be a concern.

More tired than usual – The most notable symptom is that your child is more tired than usual.
This can sometimes be hard to tell because you might think that your child is simply tired after a long day at the pool or the beach.If your child seems excessively tired, more than you might think would make sense, more than you think is reasonable for the activity they have done and especially if it’s occurring after your child had a notable coughing spell while in the water, then it would be worth a call to your NHS direct.

Chest pain – Any significant chest pain after a pool-related coughing event should be a worry, it might indicate difficulty in breathing or a feeling of fullness in the lungs. So might tummy pain, because children will often complain that their tummy hurts when the real issue might actually be in the chest.

If you are concerned about your child after a significant spluttering incident in the pool, and they show any of the above symptoms, contact NHS direct or a doctor if on holiday.

Monitor the adult or child for up to 3 days after a significant sputtering incident.

These circumstances are very rare, but being informed is our best defence.