Source of biblical flood water?

The following diagram shows how the moon causes tides on Earth:
In this diagram, you can see that the moon's gravitational force pulls on water in the oceans so that there are "bulges" in the ocean on both sides of the planet. The moon pulls water toward it, and this causes the bulge toward the moon. The bulge on the side of the Earth opposite the moon is caused by the moon "pulling the Earth away" from the water on that side.

Earth has a pull of gravity, keeping the Moon in its orbit, but the Moon's gravity, although only one-sixth the strength of Earth's, still has an effect on the Earth. This can be seen mostly with tides. Water, being fluid, is attracted by the Moon's gravitational pull, enough to pull it slightly towards it. This causes tides. Earth's gravity pulls the water back. At the same time, the Sun's pull of gravity is attracting water. So, everyday, there are two high tides on Earth, one of them caused by the Moon's gravity, the other caused by the Sun's. The highest tides are when the Sun and the Moon are aligned so they are on the same side of the Earth.

High tides are produced in the ocean waters by the "heaping" action resulting from the horizontal flow of water toward two regions of the earth representing positions of maximum attraction of combined lunar and solar gravitational forces. Low tides are created by a compensating maximum withdrawal of water from regions around the earth midway between these two humps. The alternation of high and low tides is caused by the daily (or diurnal) rotation of the earth with respect to these two tidal humps and two tidal depressions. The changing arrival time of any two successive high or low tides at any one location is the result of numerous factors later to be discussed.