[sithcdw (OP)]

Ok, simple answer to this would be "gravity"; but how?
How can the moon generate enough gravity to "pull" and move TRILLIONS of gallons of water? Why is it that the moon can move such enormous amounts of water on a daily basis but it cannot move a person? or a grain of sand?

[Soul Surfer]

Because the water is very easy to move!   There are earth tides as well but they are quite small because the earth is much stiffer