Do those who profess to believe the stories in the bible actually believe in them?

I find it incredulous that those who say they believe Genesis, and all the stories of miracles throughout the Old Testament actually do believe them. Even if they give them a different interpretation, parables if you will, they seem so far fetched from reality as to make it all seem nonsensical. The story of Jonah is a good example, to be swallowed by a fish and then spat out on dry land because he disobeyed God. Couldn't those who wrote the story think of a better plot, even if people living in 785 BC were so gullible as to be taken in by it. And how do believers living today interpret such stories. If God did conceive Jonah in men's minds as a parable and not a real person, and to become part of scripture, did he err in making it even more difficult to believe or understand in today's more enlightened world? Do modern people really believe these stories, parable or not, have any worthiness in today's world?