Ships’ Biscuit. A rock solid confection of flour and water and salt. Baked at least twice for extra solidity.
However, it fed the world’s most powerful Navy for a pretty long time.
But, it can’t have been much fun. You can’t see Nelson, Collingwood and Sir John Jervis sitting down for a cup of tea and a hard tack. Or even Admiral Duncan at the Battle of Camperdown (I mention him because we are related and it is good to brag occasionally.)
They were usually soaked in salty water and mushed into a sort of porridge.
No wonder they had fewer teeth in those days.