Update from my original review:
This past weekend I was about to jump off a high rock into a swimming hole. I took these babies off and set them on the ground next to me. Unfortunately I didn't secure them very well and next thing I saw was the glasses cascading down the rocks into the pool of water, and sinking to the bottom. After about 20 minutes of trying to search the bottom I gave up.
I just bought my second pair because even at this price, they are totally worth it and I can't seem to live without them in the summer.