According to Wikipedia [1], the codebooks were printed in red water-soluble ink. If a German ship wasn't already full of water by the time the Allies gained acc

According to Wikipedia [1], the codebooks were printed in red water-soluble ink. If a German ship wasn't already full of water by the time the Allies gained access to it, any German soldier could simply splash water (or blood) on the codebook, rendering it useless. [1] https://en.wikipedia.org/wiki/Enigma_machine#Details https://en.wikipedia.org/wiki/Enigma_machine#Details