You are suppose to avoid the sharks :p. You can use the harpoons as more of a "safety net" against them but the overall goal is to completely avoid them. The brown bag's purpose is to be an assortment of bonuses (positive and negative) to add some additional random elements to the game. It is completely optional to the game play and a not required to win the game.
*humming* hey whats that... better get out my giant butcher knife. hmm... whats up with the green ones they die so easily. hey whats that blue one do... hey it just got bigger. HOLY CR-*splat*
What's wrong with the comment section? Why should I add that to the game?