Exactly that's the one involved. So basically if Cozumel is a port of call you will not be able to go with a Royal Caribbean excursion to Main land. However you could take a ferry by yourself.
This event's are rare, very rare in Mexico. We are having drug related problems, drug cartels and other insecurity issues but never had explosives or bomb related events.
I don't think this would evolve in something worst. It feels like its some kind of political related events. The ferrys involved were property of former Governor so...
In Cozumel there hasn't been any kind of insecurity issues so far, so if you want to get off the ship you should be fine!