iron golems should naturally not want to path into water unless chasing something
and when submerged do not rust crack or drown.. 
when in water they (if not chasing something) should panic and try to get out of water.. 

i realise they are dumb machines but  in my villages near water .. they seem to all go to the water and never come out causing lag and a LARGE quantity of iron golems just sitting on the river floor
and not able to see mobs outside the water anymore.. 

(this said villagers should also not path over campfires or anything that would hurt themselves ( droppign mroe than 2 blocks for example) unless in a panic and can see a way not to be stranded
they need slightly better brains ( nitwits can be an exception))
quite often at night theres one to three villagers who have a bed but refuse to sleep and just stand in one spot taking beatings