It's so strong, it does not break,
It's so powerful, it penetrates a lake,
Sometimes it's weak as a twig left out in the sun,
It's so wonderful it gives us the power to have fun.
What is it?

Answer:

Try another Brain Teaser:

A man went to sleep and he turned off the light. The next day when he woke up there were many dead people due to his actions the night before?