When using a polarizer, it works best when the reflection/glare is coming in at a 90-degree angle to the lens. So, if it doesn’t appear to be working well, try moving around a bit. Also, for anyone that has never used a polarizer, you need to compose the image, then rotate the polarizer until the image (as seen through the viewfinder) is at its darkest point; this will be the maximum point of removal of reflected light. Personally, I like to vary the amount of polarization in an image by first rotating to the darkest point, then backing off just a bit. To me, this gives a better and more natural looking sky.