I recoded my server modifications armour as it has a very straightforward - but easilly awkward looking mechanic in default barotrauma.
How it works is per 1 armour, subtract 1 bleeding damage and 1 standard damage from anything that hits a limb.
if multiple limbs are hit at the same time however, the armour is counted from the same parts again (such as waist+torso) which easilly throws damage off for things like diving suits, which if hit in the right spots will instead of counting say 10, count 20 or 30 armour value on hit, which then subtracts 20 to 30 damage and 20 to 30 points of bleed damage looking like you take no damage at all.
Some areas of the diving suit, such as the feet or head regions seem to not even fully cover the limb despite it being 360 degree coverage, I'm not sure if this is the code not fully covering it or if its based off the sprite or what - but its possible to hit a limb that is covered and deal the full damage (Which is also often the case with diving suits)
Armour has a secondary value to define the degrees range armour covers, creatures like the crawler and moloch use this but I've never fully looked into how that works.
It's worth noting any documentation on how armor works is completely wrong, as it states the following:
Which is not the case.