Bomber Eyewear http://www.bombereyewear.com/
has some really good looking glasses that will actually float, and Knockaround http://knockaround.com/
makes really nice, super cheap glasses. I own glasses from both brands, and have Maui Jim and RayBan. I usually prefer the Knockarounds because there is really no worry as to losing them or breaking them because they are $15-25, and the Bombers will float if they slip off, and are super comfortable because they are lined with foam. Things I can't say for the more expensive shades.