Eldarian Emergency Armor

This flexible armor is made from a strange,
otherworldly material. When attuned and worn
under existing armor, the user can take a bonus
action to pull a string that quickly inflates
Emergency Armor.
When inflated, the user immediately becomes
buoyant, takes half fall damage, and gains
+1 AC. Armor deflates and loses effects after
5 minutes or at will, or after taking 4 damage.