The packing of the various named marine products at sea as an incident to, or in conjunction with, the fishing operations of the vessel is an exempt operation. The term “packing” refers to the placing of the named product in containers, such as boxes, crates, bags, and barrels. Activities such as washing, grading, sizing, and placing layers of crushed ice in the containers are deemed a part of packing when performed as an integral part of the packing operation. The packing operation may be a simple or complete and complex operation depending upon the nature of the marine product, the length of time out and the facilities aboard the vessel. Where the fishing trip is of short duration, the packing operation may amount to no more than the simple operation, of packing the product in chipped or crushed ice in wooden boxes, as in the case of shrimp, or placing the product in wooden boxes and covering with seaweed as in the case of lobsters. Where the trips are of long duration, as for several weeks or more, packing the operations on fishing vessels with the proper equipment sometimes are integrated with first processing operations so that together these operations amount to readying the product in a marketable form. For example, in the case of shrimp, the combined operations may consist of the following series of operations—washing, grading, sizing, placing 5-pound boxes already labeled for direct marketing, placing in trays with other boxes, loading into a quick freezer locker, removing after freezing, emptying the box, glazing the contents with a spray of fresh water, replacing the box, putting them in 50-pound master cartons and finally stowing in refrigerated locker.