Is it permissible to eat wild ducks hunted with a rifle that fall into the water, and is this considered among "water fowl that are not killed by water" mentioned in Ibn Qudamah's book "Al-Mughni"?

Wild ducks that fly and cannot be caught are considered permissible game and do not require ritual slaughter (dhabh). If one falls into water after being hunted, it does not affect its permissibility, based on the Prophet's (peace be upon him) saying: "If you find it drowned in water, do not eat it."

As for domestic ducks, they are not game; rather, they must be ritually slaughtered (dhabh) because they can be caught. Ritual slaughter is divided into voluntary (ikhtiyariyah) for animals that can be caught, and necessary (idtirariyah) for animals that cannot be caught, such as game.