Kids especially need to be watched closely, but more importantly - adults need to know what to look for.
There is statistic in the article where about 1/2 the kids that drown, do so within 25yds of a parent or other adult!
As the articles point out, most of what you see on television is NOT the way someone looks when they are drowning.
PLEASE take 5 minutes to educate yourself.
WARNING - the video in the first article is staged, but it could be upsetting to some people. Parents should use discretion before letting kids watch.
Short article with very effective demonstration video:
Longer article (no video):