29 C.F.R. § 783.42

An “American vessel” on which employment as a seaman is subject to the minimum wage under the provisions of section 6(b)(2) and section 13(a)(14) is not limited by the language of the Act to those vessels which are “documented” or “numbered” as described above in §§ 783.40 and 783.41. Since the term “American vessel” has traditionally been applied to regularly documented vessels (see U.S. v. Rogers, 27 Fed. Cas. 890; Badger v. Entierrez, 111 U.S. 734; 18 Op. A.G. 234 (1885); 48 Am. Jur. 40), the inclusion of numbered vessels in the statutory definition of “American vessel” would indicate that the work “includes” is used in the sense of “embracing”, as an enlargement and not as a word of limitation. The term may therefore apply to other vessels that do not fall within the illustrations given. For example, neither the documenting laws nor the numbering laws apply to vessels plying the purely internal waters of a State which do not join up with navigable waters touching on another State (19 CFR 3.5(a)(4); 33 CFR 2.10-5), but, nevertheless, the Fair Labor Standards Act does apply in those areas and it clearly would not comport with the remedial purpose of the Act to exclude from its minimum wage provisions seamen engaged in commerce or in the production of goods for commerce in those areas though the vessels are not documented or numbered. On the contrary, the legislative history shows the affirmative purpose to improve, though to a limited extent, the status of seamen (Sen. Rep. No. 145, 87th Cong., 1st sess., p. 32, 50).