29 CFR §783.31

In accordance with the legislative history and authoritative decisions as discussed in §§ 783.28 and 783.29, an employee will ordinarily be regarded as “employed as a seaman” if he performs, as master or subject to the authority, direction, and control of the master aboard a vessel, service which is rendered primarily as an aid in the operation of such vessel as a means of transportation, provided he performs no substantial amount of work of a different character. This is true with respect to vessels navigating inland waters as well as ocean-going and coastal vessels (Sternberg Dredging Co. v. Walling, 158 F. 2d 678; Walling v. Haden, 153 F. 2d 196, certiorari denied 328 U.S. 866; Walling v. Great Lakes Dredge & Dock Co., 149 F. 2d 9, certiorari denied 327 U.S. 722; Douglas v. Dixie Sand and Gravel Co., (E.D. Tenn.) 9 WH Cases 285). The Act's provisions with respect to seamen apply to a seaman only when he is “employed as” such (Walling v. Haden, supra); it appears also from the language of section 6(b)(2) and 13(a)(14) that they are not intended to apply to any employee who is not employed on a vessel.