As a miracle apart from natural law, yes.
Miracles are supernatural events, yes.
As per natural law it is not.
Supra.
In other words, science does not match scripture in that case,
Except that it does. It says it's not possible, naturally. That's why a SUPERnatural Creator is required.
See, science DOES agree with the Bible.
so I don't try to make science and scripture match up.
You should do it more often.
Then make science line up with a supernatural virgin birth.
Supra.
The discussion veered into science lining up with scripture, so no it's not mixing apples and walruses.
There's a difference between science lining up with scripture (what we're attempting to do) and saying that an event recorded in scripture didn't happen according to natural laws, where no miracles (supernatural events) are recorded (which is what you're doing).
There are several supernatural events in scripture that do not line up with science.
So what? That doesn't mean that ALL extraordinary events are therefore supernatural.
If you want to believe the flood was not a supernatural event it's OK by me, but don't begrudge me for believing it was supernatural.
I will when you assert that it was a supernatural event when it's not described as such by scripture. That would be changing what scripture says.
Wish I was there to witness how it happened.
Try the next best thing, Bryan Nickel's videos.
I have no idea if all the water that caused the flood preexisted.
The Bible says it does.
I lean towards the waters coming from below (fountains of the deep bursting open) and above (the windows of heaven and/or the storehouses mentioned in scripture) which would mean the waters already existed.
The Bible says that the waters came up from below the ground, and then fell back from the sky.
Think about what happens when you put a portable vertical sprinkler in a pool, then turn the water on. At first, you have the water shooting up into the air, then it falls back down to the ground, and slowly fills up the pool. Eventually, the water levels get high enough where the spray from the sprinkler starts to decrease, because it has to push pater through the already existing water. Then, eventually, there's no more downpour, because the force of the sprinkler can't push the water through the already present water levels, yet the water keeps rising.
That's an analogy of what happened during the flood, but it was on a much larger scale.
But I don't rule out that God could have created more water for the event.
The Bible doesn't say He did, so why speculate?
I leave that option open as a possibility.
It's not a possibility, from the perspective of the Bible.