Rays are related to sharks. Bat rays are bottom feeders with a poisonous tail sting, which like shallow sandy or muddy bottomed water.
Seen June 11th 2005 (June2005) in Richardson Bay (shallow muddy bottom). Saw the "wing" tips emerging from the water when the ray changed directions.
(Originally http://userwww.sfsu.edu/~halmark/Bat_Ray.jpg)