There are many articles on drowning and drowning prevention on the internet these days, but one of the best articles on layers of protection around aquatic facilities is by The National Drowning Prevention Alliance.
The article is so truthful and complete, I will not add anything to it but my high recommendation that you read it for the safety of your children, your students, your family and friends.
Here is the link :
http://ndpa.org/home/resources/safety-tips/layers-of-protection/
