Section 9(4)(c) in The Merchant Shipping (Maritime Labour) Rules, 2016
(c)any charge for the service under sub-rule (3) and clauses (a) and (b) of sub-rule (4) shall be reasonable in amount, and unless otherwise provided the rate of currency exchange shall be at the prevailing market rate or the official rate prescribed by the Reserve Bank of India and not be unfavourable to the seafarer.