NavList:

Peter Mota said, "The only other thing I noticed is that the guy on the left is using quite a dark horizon shade.  Either there's a lot of glare on the wavetops or there's some artistic license there."

Well, there is glare off the wave tops and both mariners have dark horizon shades up, so if it is artistic license, at least it is consistent. The details of the octant seem authentic. See https://www.deutsches-museum.de/en/collections/transport/maritime-exhibition/octant-by-janet-taylor/ for a "typical" octant with which to compare it. The only small question mark is the angle of the horizon shade - should it be vertical...?

The index arm is more-or-less vertical, so the sun will have an altitude of about 45 degrees. Evidently, there is a hole in the clouds (like the one in the picture) through which the sun is shining. The sun's reflection off the wet clothes of the mariners would seem right for that scenario. 

Would the mariner have his left hand on the tangent screw rather than resting the arc in his hand as shown? I think that is a matter of personal preference. Having reached the point of maximum altitude, the mariner may well shift his hand to a position where there is a little more stability in holding the octant while he waits for the altitude to start diminishing.

All-in-all, it seems a perfectly authentic picture. I have a photograph of my father in a very similar scene, taking the noon sight with other officers on a Royal Mail ship run down to South Africa.

Frank will no doubt illuminate us on this picture's grevious faults...?