law: 20. Power to exempt.-
  (1) The Board may, by order in writing, exempt any seaman to whom this Act applies and his employer from the operation of all or any of the provisions of this Act if, in the opinion of the Board, the seaman is in enjoyment of benefits in the nature of provident fund or pension and such benefits, separately or jointly are on the whole not less favourable to the seaman than the benefits provided by or under this Act.
  (2) Where an exemption has been granted under sub-section (1), the employer shall not at any time after the grant of the exemption, without the leave of the Board, reduce the total quantum of benefits in the nature of provident fund, pension or gratuity to which the seaman was entitled at the time of grant of such exemption.
  (3) Any exemption granted under this section may be cancelled by the Board, by order in writing, if the employer fails to comply with the requirements of sub-section (2): Provided that no such order shall be made unless the employer has been given a reasonable opportunity of showing cause against the proposed cancellation.