http://www.nrsweb.com/Safety_Tips/dry_drowning.asp

An interesting read!

The other medical condition known as "dry drowning" can occur when someone is rescued from the water, appears recovered and goes home for a hot bath and a good sleep. Sometimes - they don't wake up again !!!!!!! The lungs, having been irritated during the dunking episode attempt to soothe themselves and fill with body fluid - which is why someone who has had a dunking should ALWAYS go or be taken to hospital.

Nigel