Will vs Shall

Will - you want to willfully do something

Shall - you are going to do something because you are under and obligation

A foreign tourist was swimming in an English lake. Taken by cramps, he began to sink. He called out for help:
“Attention! Attention! I will drown and no one shall save me!”
Many people were within earshot, but, being well-brought up Englishmen and women, they honored his wishes and permitted him to drown.