If you can view this, here is a video of a sting ray. It is not easy to determine in this video, but it was surfing in the waves! It would swim out a bit and then ride the wave in about 4-6 feet. It was very intentional and brought a smile to my face as i watched them over and over again. If nothing else, you can hear the very small waves soothingly in the background.
Stingray in the surf - July 2012