Thought this was a fantastic article on drowning.
http://www.slate.com/articles/health_and_science/family/2013/06/rescuing_drowning_children_how_to_know_when_someone_is_in_trouble_in_the.html
http://www.slate.com/articles/health_and_science/family/2013/06/rescuing_drowning_children_how_to_know_when_someone_is_in_trouble_in_the.html