Fort Flagler Campground on Marrowstone Island offers 116 campsites split between a forested Upper Campground (tent/small RV sites, seasonal May-September) and a year-round Lower Campground with 55 full-hookup sites accommodating RVs up to 50 feet, all with beach access on 3.

6 miles of Puget Sound shoreline.

The single-lane boat launch ($7/day) provides access to Admiralty Inlet for fishing and paddling, with 256 feet of seasonal moorage and three Cascadia Marine Trail campsites ($12/night) available; kayak and paddleboard launches are directly from the beaches.

Reservations are required April-October (book 9 months ahead) and strongly recommended year-round, with a $10 daily Discover Pass required for entry.