Which mark does NOT indicate a hazard?

A Safe Water Mark is designed to indicate fairways and safe water, meaning it signifies areas where vessels can navigate without encountering hazards. This type of mark provides information about navigable waters, often indicating the presence of a channel or a safe route. Since its primary purpose is to guide vessels safely, it does not represent a hazard.

In contrast, the other marks mentioned are specifically designed to warn mariners of potential dangers. For instance, South Cardinal Marks and West Cardinal Marks are used to indicate the safest navigable water surrounding potential hazards, while an Isolated Danger Mark signals a specific hazard that may be present in an otherwise navigable area. Thus, those marks serve the purpose of alerting navigators to hazards rather than indicating safe passage, reinforcing that the Safe Water Mark is the only one in the list that does not denote a hazard.