Thanks. Well the trip in question with the official tour guide of the mayan ruins in question is half the price of the "boat sponsored" one. Apparently though they're not allowed inside the port.
I do wonder if you'd end up on the same bus anyway?
Its 60 mins away, 2 hours at the place, hour back - plan to be back at the boat 2 hours before it goes so there is slack there.
Thinking about it - and read somewhere else - if these tours ever did not get someone back, it'd be all over the internet, and they're business would fall apart overnight. I guess its in their interest of course to make sure nothing happens!
I did read about a story about a trip where there was a landslide or something and the road back was blocked. The boat even went without people on the "boat" trip. Thinking about it as well - if theres a major road incident, even the official "boat" trip bus is going to get stuck as well.
I think in this case the cruise company paid for hotels/onward travel (which would not happen on the private trip I guess) but I can imagine they made every effort to wait for everyone.