This sign indicates a MARSEC Level 1. "MARSEC" stands for Maritime Security, and these levels were established by the U.S. Coast Guard under the Maritime Transportation Security Act of 2002 (MTSA) to align with the International Ship and Port Facility Security (ISPS) Code.

There are three MARSEC levels, each corresponding to a different threat assessment:
* **MARSEC Level 1:** This is the normal, baseline level at which ships and port facilities must always operate. It signifies that there is no identified security threat. Standard security measures are in place.
* **MARSEC Level 2:** This level is declared when there is an increased risk of a security incident. Additional security measures, beyond the baseline, are implemented as a precautionary response.
* **MARSEC Level 3:** This is the highest level, declared when a security incident is probable or imminent. The most stringent security measures are put into effect, and access to vessels and facilities is severely restricted or denied.

The text on the sign also makes it clear that anyone boarding a vessel or entering the facility is giving their consent to security screening or inspection. Refusal can lead to denied authorization, citing specific federal regulations (33 CFR 104.265(f)(3) and 33 CFR 105.255(f)(3)). These regulations outline the requirements for vessel security plans and facility security plans, respectively, including provisions for security measures and consent to screening.