Was the blood in the water real?
Recent photos of dolphins being slaughtered by Japanese fishing crews showed the water bright red with blood. This photo may have been, um, enhanced, for effect.
A more interesting question is: is it OK to “enhance” real evidence, if the salient facts are true? Or even, more radically, if the cause is just and dedicated to save lives or relieve suffering?
Only if you tell them. Otherwise it’s the same as making up a news story then reporting it as truth.