I am new to underwater DSLR photography and I just got a housing for my Canon 50D. Now I am looking into getting a good all around lens to start with. From what I've read, the Tokina 10-17mm fisheye seems to be a favorite for underwater. I also found a good deal on a Canon 8-15mm fisheye. Any advice on which is the better choice? Taking into account the sensor on the 50D. Or suggestions on a better lens to start with?