This is a model of a bull shark made in Maya 2011. It is rigged and easy to animate along a spline path or manually if you want.
It has an auto swim feature that can be adjusted in amplitude and frequency on the main mover node attributes.
The curve of the body can also be adjusted left/right, up/down and twist on the main mover node attributes to make it swim round tight corners.
The joints can also be positioned manually using the section curves independent of the automated animation.
UV textured and rigged model provided. No backgrounds.
I used mental ray, but can render how you want.