Concessionaires and their employees aboard a vessel ordinarily do not perform their services subject to the authority, direction, and control of the master of the vessel, except incidentally, and their services are ordinarily not rendered primarily as an aid in the operation of the vessel as a means of transportation. As a rule, therefore, they are not employed as seamen for purposes of the Act. Also, other employees working aboard vessels, whose service is not rendered primarily as an aid to the operation of the vessel as a means of transportation are not employed as seamen (Knudson v. Lee & Simmons, Inc., 163 F. 2d 95; Walling v. Haden, 153 F. 2d 196, certiorari denied 32 U.S. 866). Thus, employees on floating equipment who are engaged in the construction of docks, levees, revetments or other structures, and employees engaged in dredging operations or in the digging or processing of sand, gravel, or other materials are not employed as seamen within the meaning of the Act but are engaged in performing essentially industrial or excavation work (Sternberg Dredging Co. v. Walling, 158 F. 2d 678; Walling v. Haden, supra; Walling v. Bay State Dredging & Contracting Co., 149 F. 2d 346; Walling v. Great Lakes Dredge & Dock Co., 149 F. 2d 9, certiorari denied 327 U.S. 722). Thus, “captains” and “deck hands” of launches whose dominant work was industrial activity performed as an integrated part of harbor dredging operations and not in furtherance of transportation have been held not to be employed as seamen within the meaning of the Act (Cuascut v. Standard Dredging Corp. 94 F. Supp. 197).