Foxy's does water taxis that will take you to Great Harbour, where Foxy's Bar is located. $90 a person based on 4 passengers. You'll have to get yourself to Red Hook first. Foxy has been doing business in JVD for a long, long time.
http://www.foxyscharters.com/water-taxi/
There's also Dohm's water taxi. Their rates on their site are old, but it might be worth it to give them a call.
http://www.virginislandswatertaxi.com/map.html
Dolphin Water Taxi goes from Red Hook to JVD also.
https://www.dolphinshuttle.com/
https://www.dolphinshuttle.com/destinations/day-trips-to-jost-van-dyke
There's also always the option of renting a boat (it comes with a captain).
http://stthomasboatrental.com/
The biggest problem is that JVD is not usually a big stop for water taxis and ferries from St. Thomas, and most (and perhaps all) do not leave from Charlotte Amalie. Many of the other islands (Tortola, Virgin Gorda, St. John, etc.) have regular ferries, but JVD is so small and specialized that you almost have to charter transport unless you go to Tortola, get a taxi to West End and then catch the ferry to JVD.
I'm also unsure as to whether or not the little Customs house on JVD is back up. It was hoped to be back by the end of 2017, but, well, island time and all that. If it's not up, you'll have to go through Tortola anyway to get through BVI customs.
It's about a 30-45 minute run to JVD from Red Hook.
