(a) As used in this section, "maritime employment" means employment in connection with the construction, repair, loading or unloading of vessels, and in connection with the handling of cargoes for vessels. The secretary shall, after a study of previous employment records and after investigation and hearing, determine, and may thereafter from time to time redetermine which industries are maritime industries within the meaning of this section. Until such determination by the secretary, no industry shall be deemed to be a maritime industry.

(b) The term "maritime worker" means an employee who is customarily or regularly employed in "maritime employment," such as men engaged in the construction or repair of vessels and in the operation of plants at which vessels are constructed or repaired, and it shall include longshoremen, dock workers, harbor workers, and other employees in occupations which, after the secretary has studied the nature thereof and the employment record of workers engaged therein, are found to be occupations in which employment regularly continues throughout substantially all the year.

(c) The provisions of Section 25-4-72 shall in all respects govern the benefit rights of a maritime worker, except that the weekly benefit amount of such a worker shall be determined from "the average quarterly earnings" paid such worker during his base period, instead of from the "average of the wages for insured work paid to him during the two quarters of his base period in which such total wages were the highest." If a "maritime worker" has not been engaged in maritime employment for substantially the whole of his base period, the secretary shall determine his average quarterly earnings on the basis of his earnings during the time he has actually been engaged in such maritime employment within his base period.