Section 103(1)(d) in The Merchant Shipping (Shipping Office Forms) Rules, 1963
(d)when a substitutes is engaged in the place of a seaman who has duly signed the agreement and whose services are within twenty-four hours of the ship's putting to sea lost by death, desertion or other unforeseen cause, the engagement shall, if practicable, be made before a ship puts to sea, if practicable, and if not, as soon afterwards as possible, cause the agreement to be read over and explained to the substitute; and the substitute shall thereupon sign the same in the presence of a witness, who shall attest the signature.