UPDATE: I finally got a phone number to call (it's the emergency travel department) and the nice lady said "we do this all the time". Interestingly, they wanted the documents as JPEG or TIFF files, not PDF. I found an online app that converts things. Within minutes I got a Burial At Sea Request receipt with my name, cruise, cabin, etc. and the scheduled date for the tossing of the container.
Instructions are:
Ashes must be in an approved scattering or biodegradable urn and the entire urn must be tossed. A certificate proving the urn is biodegradable may also be required.
Guest will need to provide the death certificate and cremation certificate.
Upon boarding, contact the Front Desk to set up a time and place for the this request.
Right - approved by whom? Do certificates from other countries need to be officially translated? Apostilled? So many questions and not much time.