The Canon EF 500mm f/4L IS Prime. I don't own this lens (it retails for $5500!) When we arrived at the Bai it was there, available for use, which made me very glad I had a Canon EOS SLR. With the teleconverter installed this setup has a 700mm focal length (digital crop factor on my Rebel XTi makes this a 1120mm 35mm equivalent).

Big bull elephant at the Bai.

Yup, definitely a bull elephant. He kept splashing his foot up in the water, which is (I believe) a dominance display.