Amalie Car Rental. Their jeeps can go to St. John. Amy is wonderful to work with - they pick up/drop off at the airport and you may be able to talk them into meeting you at a marina.
Paradise will pick up/drop off at marinas. Not sure about their inventory (type of vehicles) or policies for taking vehicles to St. John.
If you want to spend a day and early evening in St John you’re better off leaving your rental at the Red Hook ferry dock and take the passenger ferry that leaves every hour and get a day rental in Cruz bay. The car ferries are slow and you’ll waste time loading and reloading your car. There’s a substantial savings taking the passenger ferry which will make the St John rental a bargain.
