I guessed I should have explained myself better. This is Wes from 18 degrees north, and of course we have Ernesto. I was just worrying about having to go to town each time a guest wanted to snorkel @ Mexico Rocks. I think that you answered my question with the comment about bulk tickets. I was worried that like some parks here in the USA where there are daily limits on visitors and I was thinking that they were day of purchase only tickets.
WWIII, you might have a problem, I'm not sure how it will be handled by Hol Chan. Its my understanding that like Hol Chan your not allowed with out a licensed Tour Guide.Someone please correct me if I'm wrong but I have to buy a special permit for each of my boats to go there and can't go with out a licences Tour Guide and not just one. I have to have one for every eight tourist and another for different activities such as diving and snorkeling.
So in theory If I have 12 tourist and 10 are snorkeling with two diving, I'm required to have three licensed tour guides in the water and my personal rule is never leave the boat unattended so I've got 4 paid professionals on a trip like that.
Tickets are sold in Bulk to Tour Operators for people they are sending with Guides.
You may have a problem.
AmbergrisCaye.com 
