Food for the Long Voyage
The ship's biscuit, commonly known from the 19th century as hardtack, was developed with exploratory voyages that began extending beyond the normal length of time bread or flour could be preserved at sea. Essentially baked patties of flour, with a little salt for flavor if the crew was really lucky, the biscuits were very hard, but were easy to store and kept well on long voyages. Eating them was a chore, however, as they could not be readily consumed as-is. Breaking them up and either reusing the flower for further baking, or soaking the biscuit in a liquid, such as broth or grog, were commonly the main methods of consumption. The use of the biscuit diminished in the late 1800s, as improved methods of storing food aboard ship became readily available.
If you're interested in making your own, I used two cups of flour and one cup of water, mixed with a dash of salt. knead the water into the flour, then make patties no more than 1/2" thick. Put those on a baking sheet, poke some holes in them to help let the moisture out, and throw them in the oven at 350o Fahrenheit/177o Celsius for two hours. They don't rise (no yeast), so just make sure they don't burn. Re bake for longer term storage.