BOSTON (AP) — It's opening day for the Boston Harbor Islands.

The Boston Harbor Island Alliance, in partnership with the National Park Service and Massachusetts Department of Conservation and Recreation, is offering free ferry tickets to Georges Islands on Saturday.

Visitors will be able to enjoy a trip to the islands for a picnic, a guided tour, or just to play games in the parade ground and explore the beach.

The free ferry program is part of the National Park Service's 2015 Find Your Park campaign, to commemorate the 100th anniversary of the system next year.

The free tickets are available on a first-0me, first-served basis.

Ferries depart Long Wharf every hour from 10 a.m. until 2 p.m., and return on the hour between 1 p.m. and 6 p.m.