Genesis 7:20

Fifteen cubits upward did the waters prevail; and the mountains were covered.

1. The flood covered the mountains.
2. This reference to 15 cubits seems a bit vague, leaving me to wonder if the water level rose another 15 cubits after it had already covered the high hills, or if it rose 15 cubits above the highest mountain, or something else. It appears this has been the subject of much discussion.