Since water will seek its own level one must assume the earth was flooded to the same depth everywhere. Except it was probably a bit deeper at the equator due to centrifugal force. Since it is pretty evenly distributed, it should not cause any tilt. However, if God used his supernatural powers to make all of that water pile up on one spot; it would unbalance the world and the tilt of the axis could very well have resulted. He once made the sun stop in its orbit around the earth, so I guess He could make water pile up if He wished.

Bud