If I may suggest, perhaps a review of the rescuers testimony is needed here. I recall having read one of them on this site about the discovery of the ravine 4, and that rescuer said that the bodies of the 3 men were parallel and their heads pointing downstream. So that would mean that Nicolai was lying on his back. Possibly his head was covered by the jacket that was swollen with water? ...
(My apologies, I just don't remember whose testimony it was exactly, or which thread, otherwise I would provide the link. Will try and look it up later.)
Also, I recall that the same rescuer said that their bodies were still frozen. In one other photo of the body of Nicolai, after they removed him from the water, he is shown from the front with his arms by his side. If his body was frozen at the time, they would not have been able to bend his arms down to his side if his arms been up above his head initially. In that same photo Lyuda is laid face down beside Nicolai, and she still has her left arm up, presumably that is because her body is frozen and the rescuers were not able to fold down her arm.
One intriguing detail: of the ravine 4, three are missing their eyes (Kolevatov, Zolotarev and Lyuda), but Nicolai appears to have intact eyes, although his head was under water when found. On the other hand Kolevatov and Zolotarev looked like their head was above water. So, why are their eyes missing but not Nicolai's?