We have done GB but found they do not always run on schedule if they have guests they are waiting for. They cost more than the public ferry. You can leave the airport, get right into a taxi that will take you to Marigot. I believe the ferries run every half hour or so. We now just use the public ferry. I am not a fan of boats but in my opinion they are both about the same. Depends on the sea that day, not the captain. I was really nervous with GB but they were great with making me feel calm. I have been nervous with public ferries too but hubby (a boater) says it is the ocean not the captain. He has always felt comfortable with the boats we ride on. Also in my opinion (for next time) you will want to visit St Martin first, then Anguilla. (We have done it both ways!) Anguilla is a nice relaxation after the activity and fun of SXM!