You have nothing to eat except for two bags of chips and a package of crackers, both of which taste like gasoline. Luckily, you have some fresh, potable water, but the supply is extremely limited and the few sips you take from time to time do little to slake your maddening thirst. Your skin fries under the intense rays of an unrelenting sun and there isn't a sliver of shade to provide even a moment of relief. Add to all that debilitating hallucinations of rescuers who aren't really there. Oh, and the blacktip sharks circling beneath your capsized boat? Those are very real.