The marine products which form the basis of the exemption are the
``fish, shellfish, crustaceas, sponges, seaweeds, or other aquatic forms
of animal and vegetable life'' mentioned in section 13(a)(5). The
exemption contemplates aquatic products currently or recently acquired
and in the form obtained from the sea, since the language of the
exemption clearly indicates the named operations of first processing,
canning, or packing must be performed ``at sea'' and ``as an incident to
or in conjunction with'', fishing operations. Also, such ``marine
products'' are limited to aquatic forms of ``life.''
