There is NO ferry service to Fort Matanzas on Tuesdays.
All areas of the park are free of charge including the ferry to the fort. However, you MUST stop in the Fort Matanzas Visitor Center (NOT the St. Augustine city Visitor Center) to get your free boarding pass for the ferry. Family members of all ages must have a pass to board the ferry. Passes are Free
During operating hours, you may call 904-471-0116 and speak to someone in the Visitor Center if you do not find your answer here.
Enjoy your visit!