Well i guess it is my turn then, to begin i will also start with an overused but valid question, where did the water all go? Where would enough water to cover the earth even come from?
God can do magic, remember? Wait, I'm playing a creationist ... miracles. Not magic. Miracles. I'm sure there's a difference although if asked I'll be unable to say what it is. Anyway, since by hypothesis we're dealing with an entity that miracled the entire universe into being, he'd have no trouble making water appear and disappear.
Now at this point you may be wondering why, given that he has miraculous powers, he didn't do his genocide by just wishing everyone dead, instead of what seems to us to be a rather roundabout method of flooding the Earth but putting the animals in a boat, etc. But you must remember that according to the Bible, God's ways are not our ways, nor are his thoughts our thoughts. (See Isaiah 55.) He can do things that to us would seem stupid, evil, or psychotic, and that's just God being God, and us not understanding how awesome he is.
This means that whatever challenges you throw at me, I can invoke the existence of a being who can and who might do anything at all. I can hardly lose. If, for example, I wanted to defend the claim that the sky is green with pink spots, I am free to postulate that it is, but that for reasons known to himself, God is using his magical powers to make it look blue. By these means I can defend any position, no matter how contrary to reason, observation, the laws of physics, etc.
Meanwhile you poor saps of evolutionists have to take into account tedious questions like what is actually possible, and what the evidence shows. When will you guys admit that my way is easier?
Maybe christians just stole from the greek flood story!
According to C. S. Lewis, the reason that pagan cultures bear similarities to the One True Religion (mine, by a bit of good luck) is that God inspired them to have myths similar to the Truth.
Now in the case of the ancient Greeks you might come up with some pettifogging objection like why didn't he inspire them to not be polytheists and to not have sex with teenage boys quite so much. To which I reply Isaiah 55 again. An explanation involving God doesn't have to make "sense" to you. It only has to make sense to God. And, since we can't read God's mind, in practice that means that we only have to be able to imagine that it makes sense to God. And since we have established that his thoughts are not our thoughts, we can imagine that anything might make sense to God.