What a horrible day for this family.
This is a new concept to me that I have never heard of so I decided to look it up and find out exactly what it is. According to some sources, dry drowning is when the lungs cannot get the oxygen they need from the air. This can sometimes be due to the inhaling of water but can also happen other ways such as muscle paralysis, ogygen absorbing tissue changes, breathing in various gases, etc.
With dry drowning, it is possible to drown without any liquid involed at all like we normally associate drowning with. Accidents like these seem to be quite rare but it is something that can happen under the wrong circumstances.