Re: Fibreglass and cotton ...
> the crew in the magazine (shell storage) had to get out really very quickly indeed (up a vertical ladder) to avoid being drowned by the fire-suppression system
I believe the Royal Navy in WW2 didn't expect the magazine crews to be able to evacuate in case of a fire: they were locked into the magazine, and if it needed to be flooded then they would drown. As evidence, here is a tiny extract from a memoir by S. L. Bell, BEM, whose duty station was the 'A' turret shell room of HMS Exeter at the Battle of the River Plate:
... we all set about our work sending up prepared shells to A turret, when the ship seemed to stagger and shudder, we then noticed smoke coming down the voice pipe, and the turret wouldn't respond to calls; after a brief moment the person in charge of the shell room told the crew members there to get up top to see if there was anything that could be done to assist getting the gun back into action, as we left the shell room I asked about the personnel below in the magazine, and the PIC told me to spin the hatch to let them out and tell them what was happening, as they were locked down in the magazine in case the need to flood ever occurred.
'A' turret had been struck by a shell from Panzerschiffe Admiral Graf von Spee, but precautions against flash igniting the charges in the magazines meant that Exeter survived (just) both this hit, and many others.