Game Mechanics: "flying" mobs in water unhitable

[Bigcountry23]

This may be a limitation of the base software, but it is not something I have seen before. When a "flying" mob (Gargoyle in this case) is running away and paths into the water, it cannot be hit by melee or pets (pet seems to "freak out" and pops around under the mob as it is pathing through the water).

[Evilmorty]

This is also happening with non-flying mobs, i.e. Sisters in OOT.

[soronil]

pretty sure this is also the case in blue, so not a "Green bug"