Hiya. Being a bit of an expert in 3d rendering, I'm quite familiar with the circumstances under which reflections occur (namely, the real-world applications of Snell's Law), and I can assure you that even if we were looking at a reflective surface in this photograph, no actual reflection is possible under these circumstances.

The angle of incidence = the angle of reflection, and since all such photos are taken from straight overhead (high angle of incidence), the only thing which can be reflected is also what is straight overhead (high angle of reflection). The only thing which a reflective surface could actually reflect, from this angle, is the sky. Or possibly some clouds (which would also be visible in the picture). In order to show the reflection of the banks (or any surrounding features), the photograph would have to be taken from an extremely oblique angle (say, 10 degrees rather than 90).

Therefore it is absolutely safe to conclude that whatever one can see in this image, it is NOT a reflection.

Cheers,

Nathan.