Depending on the time you actually get on land from the tender, the boat could be an option to travel to the cayes if there is one just about to leave. But IMO DON'T rely on it for the return trip. They rarely leave on time and depending on the number of people getting on/off in Caye Caulker it can seriously delay your arrival back in Bz City. Plus if you have done the boat trip over you will only see the same on the return, so better to go back by air and see the great view from the sky instead. And leave plenty of time to get from Municipal back to the tourist village as mid afternoon you will hit the "School Rush Hour".
AmbergrisCaye.com 
