Check the link at the top right for the ferry schedule. A ferry runs once/wk from Fajardo to STT or STJ. American Eagle has regular flights from PR to STT. Usually around $100 round trip. THat's your best bet as round trip ferry is the same cost. But you'd need to get from San Juan to Fajardo and the schedule is limited.

Timothy,

There is no ferry service between San Juan and the USVI. If you use ground transportation from San Juan to Fajardo there is an occasional ferry to the USVI. At the top of this page is a link to "Ferry Schedules" which includes the following information:

St. Thomas/St. John - Puerto Rico Passenger Ferry
Transportation Services (340)776-6282
Rates: $70 one-way and $100 roundtrip
Time: 2 hours
Note: Round trip travel must be completed within the same week. Ferry service is impacted by demand, call to confirm exact schedule and time of departure. Advance ticket purchase is required.

Leaving Cruz Bay, St. John
Every Other Friday Only, 7:00 am

Leaving Charlotte Amalie, St. Thomas
Every Other Friday Only, 7:30 am

Leaving Fajardo, Puerto Rico
Every Other Sunday Only, 2:00 pm