What is the meaning of the riven mast had gone by the board?

The phrase "the riven mast had gone by the board" suggests that a damaged or split mast of a ship has fallen overboard or been lost to the sea. This imagery conveys a sense of peril and disaster, often associated with a ship in distress. It highlights the vulnerability of the vessel and the dire situation faced by those aboard. Overall, it reflects themes of loss and the unpredictability of maritime life.