USCG – United States Coast Guard
Who is covered?
A person who is on board a vessel acting under the authority of a license, certificate of registry, or merchant mariner's document. Also, a person engaged or employed on board a U.S. owned vessel and such vessel is required to engage, employ or be operated by a person holding a license, certificate of registry, or merchant mariner's document.
(Definition from Office of Drug and Alcohol Policy Compliance)
Where can I find the regulations for my designated agency?