Per Dohm Water Taxi is about your only shot, I believe. You can reach them at 340-775-6501. I believe you must still meet them somewhere which means a taxi to get to a place they can pick you up, etc. Might as well take a taxi to the ferry dock and pick up the 6 PM boat .... Ferries run every hour on the hour. Return from St. John every hour on the half hour. You might save twenty minutes or so on the private taxi.
Pamela

Hello Kim,

The Red Hook ferry runs hourly until midnight and cost $3 a person one way. It takes about 15-20 minutes. A taxi to Red Hook is necessary and takes about 35 minutes.

Dohm's will more then likely want you to come to Red Hook or East End to meet them so you will still have to take the taxi to basically the same place as the ferry.

I would say just take the ferry, if you make really good time picking up your luggage and take a private taxi (you have to request a private taxi, it will cost more, but if you don' they will wait until their taxi van is filled with others going to Red Hook or that area which could "waste" time if you are in a hurry)... you can make the 6pm ferry. The underloading of luggage in my experience is usually slow though so if you have more then one person in your group you might have one person go arrange a private taxi while the other waits for the luggage (taxi stand is right outside the baggage claim). If you miss the 6pm you will have to wait for the 7pm so if you rather avoid having to think about missing the 6pm ferry then you can look into the water ferry option.

The Red Hook St. John Ferry operates as follows:

St. Thomas to St. John
6:30 am
7:30 am
then hourly from
8:00 am to Midnight

St. John to St. Thomas
Hourly from 6:00 am
through 11:00 pm

You can view more details at https://www.vinow.com/general_usvi/interisland_ferry/

--Islander