Give a composition point about the focal point
Point: Focal point is the sunset, not the slave ship, (situated just right off the central axis in the distant background)
Reasoning: The use of contre-jour produces backlighting
Effect (1): Not only emphasises the lines and shapes present but also highlights the soon approaching nightfall, which could lead the slaves to their inevitable fate of death due to the cold water temperatures.
Effect (2): sense of depression