Most examples boil down to common sense. Nobody is going to arrest a 14 year old for driving their dying parent to the hospital.
Similarly, it is reprehensible but legal to pull up a chair and watch a child drown in a pool.
There is a difference between law and morality, and humans will use the second to selectively enforce the former.
In which country? Even for the US I don't believe the law system is that crappy.
It does not mean that you should dive and bring him back. In fact, it is not recommended unless you know what you are doing as you may put yourself in danger and need rescuing yourself. But if there are other people around who can help and you don't alert them, or if you have a working phone and don't call whatever emergency number is appropriate, than that's illegal.
EDIT: It appears that it is not illegal do do nothing in most of the US. The law only protects you from consequences of trying to help.
Really? What would be the charge?