You mentioned Symphony of the Seas cruise ship on the GM thread.
It arrived in Malaga on Tuesday and is now wending its way to various parts of Italy.
I gave mum a newspaper cutting of all the ships leaving the port and yesterday she told me about this 'ginormous boat' that she watched for a while. I reckon it was this one.
http://www.dailymail.co.uk/travel/trave ... 5a98f4c628