You have to resupply on a uncharted island
Two weeks into the projected six month journey and tradedgy strikes! The corrupt merchant to provided the food stock for the boat ripped the captain off! Most of it is spoiled and useless. The good stuff being the first gone through. The wine tastes foul and gives the men diarrhea. You catch a bad case yourself, still you must work hard. There's a stop on a island where only farmers live. The captain buys provisions and the ship sails on...
