So, essentially, graduates must sail on their license or go active duty.
I suggest you read the catalog.
However here is the wording from MARAD and the CFR
46 C.F.R. PART 310.58
(3) Maintain a license as an officer in the merchant marine of the United States for at least six (6) years following the date of graduation from the Academy accompanied by the appropriate national and international endorsements and certifications as required by the United States Coast Guard for service aboard vessels on both domestic and international voyages (“appropriate” means the same endorsements and certifications held at the date of graduation, or the equivalent);
(4) Apply for an appointment as, accept any tendered appointment as and serve as a commissioned officer in the USNR (including the Merchant Marine Reserve, USNR), the United States Coast Guard Reserve, or any other Reserve component of an armed force of the United States for at least six (6) years following the date of graduation from the Academy;
(5) Serve in the foreign or domestic commerce and the national defense of the United States for at least five (5) years following the date of graduation from the Academy:
(i) As a merchant marine officer serving on vessels documented under the laws of the United States or on vessels owned and operated by the United States or by any State or territory of the United States;
(ii) As an employee in a United States maritime-related industry, profession or marine science (as determined by the Maritime Administrator), if the Maritime Administrator determines that service under paragraph (a)(5)(i) of this section is not available;
(iii) As a commissioned officer on active duty in an armed force of the United States or in the National Oceanic and Atmospheric Administration; or
(iv) Other maritime-related employment with the Federal Government which serves the national security interests of the United States, as determined by the Maritime Administrator; or
(v) By combining the services specified in paragraphs (a)(5)(i), (ii), (iii) and (iv) of this section; and,
(vi) Such employment in the Federal Government that satisfies paragraph (a)(5)(iv) of this section must be both significantly maritime-related and serve the national security interests of the United States. “Significantly” is equated to a material or essential portion of an individual's responsibilities. It does not mean a “majority” of such individual's responsibilities, but means more than just an incidental part; and
(6) Submit periodic reports to the Administration to establish compliance with all the terms of the contract.
(b) Service as a merchant marine officer. For purposes of the service obligation set forth in paragraph (a)(5)(i) of this section, a satisfactory year of service on vessels in the United States merchant marine as a merchant marine officer shall be the lesser of—
(1) 150 days; or
(2) The number of days that is at least equal to the median number of days of seafaring employment under articles achieved by deck or engine officers in the most recent calendar year for which statistics are available.
(c) Marine-related employment. (1) Graduates who do not meet the sea service requirement in paragraph (b) of this section and who claim employment in a United States maritime-related industry, profession or marine science as meeting all or part of the service obligation under paragraph (a)(5) of this section and the serve obligation contract shall submit evidence to the Administration that they have conscientiously sought employment as a merchant marine officer, and that such employment is not available. Such evidence submitted, and other information available to the Administration, shall be considered in any finding. In view of current and projected employment opportunities afloat, the Administrator will grant the shoreside employment option infrequently and only on the basis of comprehensive evidence.
(2) The Administrator may consider positions of operational, management or administrative responsibility, including, but not limited to, the following marine-related categories, to be under the provisions of §310.58(a)(5)(ii) of this subpart and the service obligation contract: Civilian employment in Federal and State agencies related to maritime affairs; steamship companies; stevedoring companies; vessel chartering and operations; cargo terminal operations; naval architecture; shipbuilding and repair; municipal and State port authorities; and port development, marine engineering, and tug and barge companies.
By the way if you were to go Marine Engineering Systems why would you want to go work in the aerospace industry?