If it's any further help I have been to 4 different Mexican cruise ports, sailing from/to the USA, in recent years & as a Brit with a UK passport have never required an entry visa of any kind......Regards Wilba.
I think this is possibly what they are referring to ESTA which is the new part of the visa waiver program.
I would think it best if you ask the Foreign Office, or the Mexican Consulate / Embassy here in the UK or a Travel Agent of repute because I do not think it is as simple as Mr Wilba, to whom I owe some kisses, suggests. If you Google FMT Form, as I did, you will come up with a great deal of information such as:..... "An FMT is a tourist visa for people traveling to Mexico. Although this visa can potentially be valid for 180 days, the time assigned is at the discretion of the Immigration officer. Normally the time period is related to the purposes of your journey. Usually the visa is approved for a maximum period of 90 days if you arrive in Mexico by plane for a vacation, after which it can be renewed for an additional 90 days at any Mexican Immigration office. If you are crossing the border in an automobile, you can request the full 180 days. There is no guarantee that the full 180 days will be given."
It may be that this only applies to US citizens but you have the time to explore before you go although I know from experience that the Mexican authorities can be slower than the Italian ones so some urgency might pay dividends. Lucy X
Hi we visited Cozumel from a Carnival ship last week... and all we needed was our passports....I did take a notarised letter for my ten year old Grandaughter [ it cost £50 ] as this is advised for anywhere in Mexico...but needless to say it was not asked for once!!....but that was all...have a lovely cruise!