So, age mid 60's, someone drops a bombshell.
Your daddy is..... and gives a few details.
This person died in Dec 1970, on a cruise ship around Portugal, how on earth can I get a death cert?
If you can find out where the ship is registered, start with their head office. The death may have to be registered in the country where the shipping line is registered, or else the nearest next port-of-call. Or, best of all, try the British Foreign Office to see which consulate was notified.
Have you checked a family history website such as Ancestry to see if it shows up ..... are you in the UK? Was this person living in the UK at the time? If you don't have ancestry access and you want it looking up send details to [email protected]