ok, knowing sod all about fishing or underwater photography, I am making my observations based on common sense. Bendy rods and odd waterlines can very easily be accounted for by the fact that one asusmes it was shot within a camera housing and therefore it also hints at the assumption that the water would be moving across the housing viewer [I looked at a few in that shop under waterloo bridge and they seem to indicate, though I could be wrong' the glass doesn't 'blob' the water, but create a 'film' across the glass, which would more than easily cause minor distortions] BUT... my understanding is that even a smallish fish would need more than that very light looking hold on the rod in his right hand, though again, its feasible its a very small fish, taking perspective into account. No idea how small trout get. Another point that stands out is where the line enters the fishes mouth, it actually seems to stop, and there is almost what appears to be a cloned in spot...
so...imo... probably a fake, or a very very lucky capture :dunno: