Which of the following best describes the operational environment of a WIG craft?

The operational environment of a WIG (Wing-In-Ground) craft is indeed characterized by its operation in close proximity to the water surface. This unique type of vessel utilizes the aerodynamic lift generated by its wings when flying close to the water, allowing it to achieve flight while significantly reducing drag and fuel consumption. The design of a WIG craft enables it to take advantage of the ground effect, which occurs when an aircraft is flying near a solid surface, such as water.

Choosing this option accurately reflects the specific design and functionality of WIG crafts, which rely on maintaining a low altitude over the water to optimize their performance. They are not limited to deep sea travel or calm waters, and they aren't designed for high-altitude travel, as their focus is on utilizing the physical dynamics at lower altitudes in a way that is efficient and effective for transport. Thus, operating close to the water surface is the defining characteristic of WIG craft, making this choice correct.