The best that you can do is to think of some longing that has possessed you, as the longing for the sea possessed the author of Hi-Brasil. Take some prosaic character, not usually moved by such longings as your own, and show him brought strongly under the influence of a great desire. Make your story so realistic that it will seem true, and so symbolic that it will be at once poetic and capable of conveying a strong idea. Do all in your power to make your story crystal-clear, strongly outlined, and effective in power.