And in news just in this is from the Maritime Radio Handbook:
10. Secrecy of Communications
10.1 Under the International Radio Regulations, an operator and any other person who becomes aquainted with the contents of a radiotelegram, radiotelephone call or radiotelex call is placed under an obligation to preserve the secrecy of such information
10.2 Secrecy restrictions do no apply to distress, urgency or safety alerts or messages or any message that is addressed to "all stations".