A tank barge is categorized by the Coast Guard as?

A tank barge is categorized as having no means of self-propulsion. This classification is significant because tank barges are typically designed to be towed or pushed by tugboats rather than navigating independently. Their lack of a propulsion system allows for more efficient transport of bulk liquids, such as chemicals or petroleum products, across waterways. This characteristic defines their operational capacity and limits their capability in terms of maneuverability compared to self-propelled tank vessels.

The other options focus on aspects that are not defining characteristics of a tank barge. For example, not all tank barges are specifically powered by a marine engine, as they are designed to rely on external vessels for movement. Additionally, while many tank barges are indeed used for transporting hazardous or non-hazardous cargo, they are not limited to just chemicals or hazardous materials; they can carry various kinds of liquids. Thus, understanding the primary function and operational method of a tank barge clarifies its classification under Coast Guard regulations.