Continuing the discussion from What are those padded things on the bridge of a ship?:
This is the correct answer. They were mainly things like futons and other similar materials and they were specifically to absorb any shrapnel and stop it from ricocheting.
As I understand it, these were fashioned by crews on their own as a way to, as it’s called today, “up armor” positions that might reflect a blast.
I get why people think it is sand bags, but I can assure you they are not. You can’t just add that kind of weight, especially to top heavy piece like the super structure. You seriously would need to have a naval/maritime architect to make those sorts of changes.