From the Introduction:
Many disasters can strike a ship at sea. Storms, monsters, giant waves or pirates all have the potential to leave barely a trace of a ship. Whatever happened in this particular case gave the survivors at least enough time to hastily cobble together a small raft before their ship finally disappeared below the waves.
Cobbled together from planks, beams, empty barrels and parts of the rigging as it is, it is most likely only a temporary respite for the survivors. With the contents of some of the crates and barrels still afloat around the raft to aid them they might still be able to sail their piece of floating wreckage to a nearby shoreline or island. At least if wind and weather remain favourable.