Some of the US Charter companies are licensed to operate in the BVIs to take you all the way to your destination. I believe Dolphin and Ocean Dreams are both licensed. I have used Dolphin for past trips and Ocean Dreams was good to work with but Dolphin lined up better for us. Dolphin picked up our group of 6 in a vessel that could hold close to 50 people so I am sure 20 is not an issue.