While what you said was complete nonsense, I think I can show you why (assuming you weren't being sarcastic). For a complete flood, you would need the highest mountain to be covered by water. If this mountain's height was 3000M, with your reasoning, it would have 70% chance of being flooded. But the chances would be the same if the mountain was 10000M high. You get such an absurd result because you can't use probability this way. It would be like saying that a room that has a pool covering 50% of its surface has 50% chance of being flooded (by what?).
And you completely missed the point, what my message pointed out was that your probability calculus was completely off and made no sense. If you couldn't even see that, I will need to ask other members whether it is because I don't understand English well (I'm French) or you don't.
The surface of the hall which houses a pool in my city is covered by water at 70%, is that evidence one day it was totally covered by water in the past? How can you not see that there are no logical connexions between the two? The only way to argue this way would be to consider the volume of water on Earth and the amount required to flood it. The surface covered by water has nothing to do with it. Such a thing should be obvious if you ever studied geometry at high school level. I don't ever unverstand how you could use such a stupid argument.