Based on the description of the artwork as a "small raft filled with many exhausted people, all clamoring to get the attention of a ship," it sounds like this piece may likely be three-dimensional, possibly created from various materials to represent a sculptural element.
If it is indeed a physical representation (like a model or a diorama), then it would belong in the sculpture area. However, if it is instead a painted or drawn depiction of this scene, it would go in the painting area or drawing area depending on the technique used.
Given the options, if you are certain it's a tangible representation, I would place it in the sculpture area. If this artwork is a visual representation on a flat surface, then it would go to the painting area or drawing area based on the medium used.