St. John in the US Virgin Islands has no airport and thank god no cruise ship dock. So, unless you have your own boat, you will have to fly into St. Thomas (STT) or Beef Island (EIS), Tortola, BVI and take the ferry over.
Do I need a passport to go to St. John / St. Thomas
St. John and St. Thomas are U.S. territory. If you are an American Citizen you will not need a passport to visit St. John or St. Thomas (Driver’s License is fine). but it still serves as the best identification when traveling. Otherwise, you must be prepared to show evidence of citizenship when departing the islands, such as a raised-seal birth certificate and government-issued photo ID.
If you would like to visit the neighboring BVI islands like Jost van Dyke, Tortola or Virgin Gorda, you will need a passport.
If you are not a U.S. citizen, then a passport issued by your country of origin is required.
Passenger Ferry St. Thomas – St. John
The passenger ferry to St. John leaves from Red Hook, St. Thomas. You will have to take a taxi from the airport to Red Hook to catch the ferry. The price is about 10-20$ per person including luggage that is in a shared taxi with multiple people. If you are taking sports equipment like surfboards or paddleboards, they might not let you share a van and tell you you have to take one by yourself which will cost 90-100$.
The ferry ride on the passenger ferry from St. Thomas costs about 8$ and takes 20-30 minutes. The ferry runs every hour. See link below for schedule.
There also is another passenger ferry from Charlotte Amalie, which is closer to the airport, but it runs only 3x a day.
Car Barge St. Thomas St. John
Another option is rent a car on St. Thomas and take the car barge over (50$ return ticket). Like this you can stop for some basic on St. Thomas KMART and Homedepot before heading over the St. John, where groceries are very expensive. Make sure the rental company allows the car to be taken over to St. John before making a reservation.
Flying in from Tortola
If you fly into Tortola you will have to go through BVI customs and will need a passport – St. Thomas visitors from the US do not need a passport (it is however advisable to have / bring one, so that you can visit Jost van Dyke or Virgin Gorda.
The Airport is on Beef Island in the very East of Tortola and a long, expensive Taxi ride from the West End, where the St. John Ferry leaves (about 70-90$). There is limited ferry service from Road Town to St. John, which is closer to Beef Island
Flying in through San Juan, Puerto Rico
Especially for overseas visitors it can sometimes be cheaper to fly into Puerto Rico (SJU) and take a connecting flight to St. Thomas from there. Prices start from 59$ with Jet Blue (one way).
You can find the latest St. John ferry schedules here.