It's not in reference to anything at all... just the phrase, "the vessel." What does your imagination conjure when you hear those words? Do you picture a pirate vessel, filled with brigands? A earthenware vessel hand crafted by a primitive society? Do you imagine the structure known as the Vessel in Manhattan?
My best suggestion would be to use the definition and see if it spurs any ideas. In fact, I'll add it to the challenge post.
vessel, noun
1. a craft for traveling on water, now usually one larger than an ordinary rowboat; a ship or boat.
2. an airship.
3. a hollow or concave utensil, as a cup, bowl, pitcher, or vase, used for holding liquids or other contents.
4. Anatomy, Zoology. a tube or duct, as an artery or vein, containing or conveying blood or some other body fluid.
5. Botany. a duct formed in the xylem, composed of connected cells that have lost their intervening partitions, that conducts water and mineral nutrients. Compare tracheid.
6. a person regarded as a holder or receiver of something, especially something nonmaterial: a vessel of grace; a vessel of wrath.