For those not familiar with the Old Testament, this painting is based on Genesis 8:6-12:
"After forty days Noah opened a window he had made in the ark and sent out a raven, and it kept flying back and forth until the water had dried up from the earth. Then he sent out a dove to see if the water had receded from the surface of the ground. But the dove could find nowhere to perch because there was water over all the surface of the earth; so it returned to Noah in the ark. He reached out his hand and took the dove and brought it back to himself in the ark. He waited seven more days and again sent out the dove from the ark. When the dove returned to him in the evening, there in its beak was a freshly plucked olive leaf! Then Noah knew that the water had receded from the earth. He waited seven more days and sent the dove out again, but this time it did not return to him."
This incident is paralleled in the New Testament, at the baptism of Jesus in Mark 1:9-10:
"At that time Jesus came from Nazareth in Galilee and was baptized by John in the Jordan. Just as Jesus was coming up out of the water, he saw heaven being torn open and the Spirit descending on him like a dove."
Racist logic is nullified in Christ: "For he himself is our peace, who has made the two groups one and has destroyed the barrier, the dividing wall of hostility, by setting aside in his flesh the law with its commands and regulations. His purpose was to create in himself one new humanity out of the two, thus making peace, and in one body to reconcile both of them to God through the cross, by which he put to death their hostility. He came and preached peace to you who were far away and peace to those who were near. For through him we both have access to the Father by one Spirit." (Ephesians 2:14-18)
If you reflect on the symbolism you may observe that the cup or chalice is being held by a divine hand, usually representative of God or one of God's angelic messengers. Above it is a dove, symbolic of the Spirit of God, holding a communion wafer marked with a cross. From the cup flows living water, symbolising eternal life.
This is the grail, the cup of Christ. What is offered here is the life of Christ, which is life without limit. These waters never run out.