When I am shooting outdoors, I always have my circular polarizer with me. In fact, it's more often affixed to my lens than not. A polarizer is a vital piece of equipment for landscape photography.

However, there are shooting situations when I don't want the effect of the polarizer. Last weekend, I encountered one of these situations. I was at the beach, scouting where I'd setup for a sunset shot and noticed how the clouds were reflecting in the tide pools. To photograph the reflections, I needed to eliminate the polarizing effect. 

These two photos are taken moments apart of the exact same subject. The only difference is the position of my circular polarizer. In the first shot, I have the polarizer rotated to work a full strength. In the second shot, I turned it about a half-turn to eliminate the effect.

A polarizer cuts through reflections. And that's great for shallow streams, shooting through glass, and so on. It also helps if what's beyond the reflection is pleasing to look at (not exactly the case for this tide pool).

To capture the reflection itself, turn your polarizer to a neutral position, effectively disabling it. How do you how much to turn your polarizer? Turn it until the scene looks good. Yes, very scientific, I know. :)