See that is where I have to say "Machts nichts". Why? I do believe it is true (that Noah had an ark and saved a bunch of animals). I do not beleive it covered the world, and I do not beleive it was every species (just the common ones in his area). And the flood happened. But it was local, but as in those days local was the world, that was how it was written.
Did God cause the flood? That we will not know in this life. But it really does not matter. For belief is not based upon a flood or a fish. But on faith. God may be the deciding factor, and for many He is. But for me, it is the lessons of the Bible. Not the historical accuracy. So true or allegorical, it will not affect my faith.