Section 202(12)(b) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(b)From an appointment in India to an appointment ex-India and vice versa.(i)An officer transferred from an appointment in India to an appointment ex-India or vice versa, shall be granted the acting rank, if the new appointment carries a higher rank, from the date of embarkation.(ii)An officer holding acting rank in an appointment in India on transfer to another appointment carrying an equivalent rank ex-India or vice versa shall continue to hold the acting rank until the date of assumption of the new appointment or until the new appointment falls, vacant, whichever is later, but the retention of acting rank within Indian limits prior to embarkation shall be subject to the fulfilment of the conditions in Cl. (a).