The video below was shot with my GoPro Hero3 without any filters at all. On this trip, we discovered that the red filter at less than 20' of depth makes a hash of the scene, turning everything a sickly yellow. There's another filter designed for snorkeling that is only slightly red and I'm going to get one of those before our next tropical island foray.
In the meantime, this video really is best seen in full screen and HD. The lower res versions don't do the turtle justice.