First, if you are going to live the life of a sea faring individual, prior to launch, insure you have not only food and staples, extra equipment that might be used to replace damaged or lost items that help control and stabilize the craft should it be needed.
In this movie, it is clear that the seat cushions are covered with a nylon seat cover. it also showed that he had a Boat hull repair kit but no fiberglass. Instead of allowing the hull to fill with water, a windward tack that brought the opening above the water line, pump out what water was around the opening and use the epoxy resin from the kit with the nylon seat covers, this, while not aesthetically appeasing, would have sufficed to repel any further intake of ocean water until he could find safe harbor berth.
While I really don't like Robert Redford, this movies motive was to portray dire straits in a situation, not an idiot who became a victim of their own inept inactions and actions.