Squigly Squigly's Brain Teasers

Question:

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:

Light.

Try another Brain Teaser:

What kills kings,
what makes mountains crumble,
and makes all life come to an end?