26 U.S. Code § 1358 - Allocation of credits, income, and deductions
(a) Qualifying shipping activities
For purposes of this chapter, the qualifying shipping activities of an electing corporation shall be treated as a separate trade or business activity distinct from all other activities conducted by such corporation.
(b) Exclusion of credits or deductions
(1) No deduction shall be allowed against the notional shipping income of an electing corporation, and no credit shall be allowed against the tax imposed by section 1352 (a)(2). 
(c) Transactions not at arm’s length
Section 482 applies in accordance with this subsection to a transaction or series of transactions—
(2) as between an  person’s qualifying shipping activities and other activities carried on by it.
 So in original. Probably should be section “1352(2).”.
 So in original.