ZanderU wrote:

Hi all, longstanding question I have (resurfacing after I visited a
superb small steel ship): Is it true that to be truly class A
seaworthy a ship needs metal covers for (certain) windows?

Various covers are required.

At night, opaque covers protect the helmsmans' night vision, and the
nav light picture presented to other vessels. Interior lights can
confuse pilots on other vessels, and can damage night vision in deck
crew. There are blackout rules.

If a portlight is as strong as the superstructure it mounts in, no
additional covers would be required, otherwise...

A sufficiently vicious wall of water can carry away superstructure,
let alone portlights.

The only unsinkable boats are on the land, and even some of those,
the sea drags offshore to sink.

Terry K