Which of the following does NOT affect a vessel's trim?

Trim refers to the difference in the draft of the bow and stern of a vessel and is influenced by several factors related to weight and shift of mass within the vessel. The primary elements that can significantly affect a vessel's trim include the weight of the cargo loaded, which alters the overall weight distribution, and the distribution of fuel onboard, as this liquid can be shifted and repositioned within the tanks. Additionally, the speed of the vessel can also affect trim due to hydrodynamic forces acting on the hull, particularly in instances of planing or differing water flow conditions.

The presence of crew members does not typically have a substantial impact on a vessel's trim. While personnel onboard do add weight, the amount is generally negligible compared to the weight of cargo or fuel. Consequently, the number of crew members present is the factor that does not significantly influence the trim of a vessel, making it the correct answer in this context.