It's a dream. It doesn't have to be about a real event.
I think the "fingernails scratching" and "kicked off our pantleg" are taken from the Bismarck. The general setting fits the sinking of Lancastria much better (especially since it was filled mostly with non-combatants, unlike the Bismarck, which was filled with soldiers - frankly, soldiers on the side of evil - in a time of war). Maybe it was inspired by Dieppe.
The historical connections do matter a great deal, but the vividness of the recalled (imagined?) dream is what matters more. It's silly to lose sight of that while arguing which historical incident fits the song lyrics better.
It's a dream. It doesn't have to be about a real event.
I think the "fingernails scratching" and "kicked off our pantleg" are taken from the Bismarck. The general setting fits the sinking of Lancastria much better (especially since it was filled mostly with non-combatants, unlike the Bismarck, which was filled with soldiers - frankly, soldiers on the side of evil - in a time of war). Maybe it was inspired by Dieppe.
The historical connections do matter a great deal, but the vividness of the recalled (imagined?) dream is what matters more. It's silly to lose sight of that while arguing which historical incident fits the song lyrics better.