29 C.F.R. § 783.40
A vessel "documented * * * under the laws of the United States" is typically a vessel which has been registered, enrolled and licensed, or licensed by the Bureau of Customs under the laws of the United States (46 U.S.C. 11 , 193 , 251-252 , 258 , 840 ). Although Bureau of Customs regulations provide for three types of documentations, distinctions between the categories of vessels subject to them are immaterial for the purposes of the Fair Labor Standards Act, since a vessel with any of the three kinds of documentation is an "American vessel" within the section 3(p) definition. Generally, any vessel of five net tons or more which is owned by a citizen of the United States is "entitled to" documentation. Complete information on the documentation requirements may be found in 19 CFR part 3.
29 C.F.R. §783.40