It may leave from just outside of Marigot.

One year we took a cab from airport to GCBC and shared with a couple taking a cruise. The driver drove on the road by O'Plongoir across from Yacht club and took a left to a dock area. I remember it because even thou' we weren't taking the cruise, we had to show passports to get into the gated area for the couples drop off then headed on to Grand Case.