Under the water the world was so much different. There was no up or down, no left or right. There was only the pull of the currents that guided you, the steady tug of a flowing stream. All you had to decide was whether or not you would follow.
This is a bloody apple. The apple is a sign of temptation, suggesting the temptation for Grace to kill. It's also temptation of another kind, when Simon offers the starving Grace an apple and she is hiding her desire for it until she "lift(s) the apple up and press(es) it to (her) forehead" (42).