Awesome. Maybe. But also wrong.
Necrophages aren't "dead things that eat" but "things that eat corpses". It is also clearly stated in the Bestiary (if you find the correct books) that Drowners are not reanimated corpses of dead criminals, but rather an aquatic species - the "Drowned Dead" thing is a peasant superstition, similar to witchers eating children, vampirism being contagious from bites, mice coming from rotting straw and snails coming spontaneously from leaves.... all things stated within the game &/or book universe, but also with some nods towards the lack of accuracy in many things which are widely known.
Actually the Drowned Dead's are real and not the same as a Drowner. See this excerpt from The Witcher 1 where it says:
"Particularly strong and dangerous drowners are known as the drowned dead. Simple people see no difference between the drowner and the drowned dead — encountering either of them is equally deadly. We might suppose, though, that the most gloomy legends concern the drowned dead rather than drowners."
Further into the lore of TW1 it is made somewhat evident that Drowned Dead are:
Irredeemable criminals who end their lives in the waters of Lake Vizima become drowned dead, a very dangerous variety of drowner. Fate refused them a chance to amend their ways and return to society, so they remain villains after death, drowning innocent citizens.
