For all tourists travelling overseas, it is advisable to request from your travel agent, cruise company, airline and/or accommodation whether your passport will be withheld by them, duration & means of identification should an incident arise.
A recent cruise was more than upsetting when our passports were requested prior to mounting the gangplank. When asked for an explanation, we were advised "a requirement of the Indonesian Government & if you do not comply, you will not permitted to board the P&O ship."
Upon inquiry to Dept of Foreign Affairs & Trade, the following advice:-
"The Australian Passport Office advises that you should keep your passport secure at all times. It is a document accepted internationally for identity purposes and should be kept in your possession while travelling overseas. We would suggest you enquire with P&O, or any future tour company as to whether you could provide a copy of your passport so that you can retain your physical passport in your possession."
Make this part of your Travel Insurance Plan.