With the help of a dispenser, villagers can be dressed in armor and mob heads. This also transfers the effect of the armor or mob heads. If a villager wears a zombie head, the villager can get closer to the zombie without being seen than usual.
This is how the effect of a turtle helmet should work and the villagers don't lose air for 10 seconds underwater, right? However, this is not the case and the effect of the turtle helmet does not work, is that a bug?