Which of the following features does not assist navigation but indicates a specific area?

The selection related to features that do not assist navigation but rather indicate a specific area is indeed Special Marks. Special Marks are used within the IALA Maritime Buoyage System to indicate areas that have special characteristics or purposes that are not navigational hazards. They may designate zones such as those for recreational activities, fish farms, or underwater cables, but they do not provide navigational guidance or safety information like hazards or safe water locations.

Cardinal Marks, Danger Marks, and Safe Water Marks all play crucial roles in assisting navigators by providing important information about their environment. Cardinal Marks help with determining safe navigable waters relative to land, indicating the direction of safe passage; Danger Marks highlight hazards that require caution; and Safe Water Marks signal the presence of navigable waters which are free from obstructions. In contrast, the main purpose of Special Marks is simply to indicate an area rather than aiding in navigation directly. Hence, they are characterized distinctly as features that do not assist navigation.