The U.S. Coast Guard employs a three-tiered system of maritime security levels (commonly called MARSEC), designed to easily communicate pre-planned scalable responses for credible threats. Maritime security levels are most often related to potential terrorist activity. In response, ports such as that in Tacoma use the Coast Guard system, often aligned with the five-level system used by the U.S. Department of Homeland Security.

• MARSEC Level 1 means that the threat of an unlawful act against a terminal or vessel is (though possible) not likely.
• MARSEC Level 2 means that an unlawful act against a vessel or terminal is possible, and intelligence indicates that terrorists are likely to be active within a specific area, or against a type of vessel or terminal.
• MARSEC Level 3 means an unlawful act against a vessel or terminal is probable or imminent and intelligence indicates that terrorists have chosen specific targets.

Upon entry to a restricted area, the current MARSEC level is posted on site.