Which type of hybrid operation is a WIG craft specifically designed for?

A WIG (Wing-in-Ground) craft is specifically designed to operate by flying just above the water's surface, harnessing the ground effect to achieve greater lift and efficiency. This unique design allows it to transition between the characteristics of traditional aircraft and surface vessels, enabling flight at very low altitudes over water.

The focus on air and water is crucial because WIG crafts utilize their wings to generate lift while remaining in close proximity to the water, taking advantage of the increased aerodynamic efficiency created by the ground effect. This operation at low altitudes allows them to reach high speeds similar to aircraft, but within the operational environment of surface water navigation.

In this context, other options do not accurately describe the characteristics of a WIG craft. For example, hybrid operations involving land would not apply, since WIG crafts are primarily intended for operations over water and excel in that domain. Similarly, options that involve underwater operations do not align with the fundamental design purpose of WIG crafts, which focus on surface effect rather than subaquatic maneuvering. Therefore, air and water is the only appropriate classification for the operational capabilities of a WIG craft.