What type of propulsion is typically not associated with a WIG craft?

WIG (Wing In Ground effect) craft primarily operate by utilizing the aerodynamic lift generated when flying close to the water surface. Jet propulsion, conventional propeller propulsion, and hydrofoil propulsion are all methods that can be employed by WIG craft to achieve or augment their speed, lift, and maneuverability.

In contrast, sail propulsion relies on wind power to drive the vessel, which does not align with the operational characteristics of WIG craft that are designed to function close to the water's surface, where wind-driven propulsion is less effective and not practical. As WIG craft primarily exploit the ground effect it becomes clear that sail propulsion would not typically be associated with their design or operational methodology. Hence, this distinguishes sail propulsion from the other propulsion types mentioned, making it the correct choice in this context.