Question: What military fort in Maine is now a park accessible only by boat and is within site of Willard Beach?

Context paragraphs:
Fort Gorges: Fort Gorges is a former United States military fort built on Hog Island Ledge in Casco Bay, Maine.  Built from 1858 to 1864, no battles were fought there and no troops were stationed there.  Advancing military technology, including iron clad ships and long range guns, made the fort obsolete before it could be used.  The fort is now a park, accessible only by boat.  It was added to the National Register of Historic Places in 1973.

Fort Walla Walla: Fort Walla Walla is a United States Army fort located in Walla Walla, Washington.  The first Fort Walla Walla was established July 1856, by Lieutenant Colonel Edward Steptoe, 9th Infantry Regiment.  A second Fort Walla Walla was occupied September 23, 1856.  The third and permanent military Fort Walla Walla was built in 1858 and adjoined Steptoeville, now Walla Walla, Washington, a community that had grown up around the second fort.  An Executive Order on May 7, 1859 declared the fort a military reservation containing 640 acres devoted to military purposes and a further 640 acres each of hay and timber reserves.  On September 28, 1910 soldiers from the 1st Cavalry lowered the flag closing the fort.  In 1917, the fort briefly reopened to train men of the First Battalion Washington Field Artillery in support of action in World War I.  In 1921, the fort and property were turned over to the Veterans Administration where 15 original buildings from the military era remain.  Today, the complex contains a park, a museum, and the Jonathan M. Wainright Memorial VA Medical Center.

Tillicum Village: Tillicum Village is a Puget Sound area visitor attraction located on Blake Island, a Washington State Park accessible only by boat, which is off the shore of Seattle, Washington.  Argosy Cruises operates the Tillicum Excursion, a four-hour cruise from Pier 55 in central Seattle to Tillicum Village and back.

New Glarus Woods State Park: New Glarus Woods State Park is a 431 acre Wisconsin state park featuring rolling hills covered by a mix of forest and prairie.  The Sugar River State Trail connects to the park, making the park accessible by bike.  This trail also connects to the Badger State Trail.

Fort Rodman: Fort Taber District or the Fort at Clark's Point is a historic American Civil War-era military fort on Wharf Road within the former Fort Rodman Military Reservation in New Bedford, Massachusetts.  The fort is now part of Fort Taber Park, a 47-acre town park located at Clark's Point.  Fort Taber was an earthwork built nearby with city resources and garrisoned 1861-1863 until Fort Rodman was ready for service.

Pocket park: A pocket park (also known as a parkette, mini-park, vest-pocket park or vesty park) is a small park accessible to the general public.  Pocket parks are frequently created on a single vacant building lot or on small, irregular pieces of land.  They also may be created as a component of the public space requirement of large building projects.

Willard Beach: Willard Beach is a beach and neighborhood in South Portland, Maine.  The beach, which covers 4 acres, used for swimming as well as commercial and recreational boating.  Southern Maine Community College abuts the beach.  Willard Beach is known for its views of Spring Point Ledge Light as well as island forts including Fort Gorges.

South Portland Bus Service: South Portland Bus Service is a municipally-owned suburban provider of mass transportation.  Because the city of South Portland opted out of the Greater Portland Transit District, this community runs its own separate three-route bus service.  Two routes serve major shopping areas and loop through major residential streets, funneling residents locally and giving them access to downtown Portland.  A third route provides access to Willard Beach and Southern Maine Community College, with all three routes going to downtown Portland.

Fort Victoria (Isle of Wight): Fort Victoria is a former military fort on the Isle of Wight, England (grid reference [ SZ339898] ), built to guard the Solent.  The earliest fort on the site was a coastal fort known as Sharpenode Bulwark built in 1545-7 by Henry VIII, but these defences had fallen into disrepair by the 17th century.  Fort Victoria was built in the 1850s.  It was a brick-built triangular fort with two seaward batteries meeting at a right angle.  It remained in use until 1962.  Parts of the fort were subsequently demolished, and what remains has become part of Fort Victoria Country Park.

Gauley River National Recreation Area: The Gauley River National Recreation Area, located near Summersville, West Virginia, protects a 25 mi portion of the Gauley River and a 5.5 mi segment of the Meadow River in southern West Virginia.  Little of the park is accessible via roads; one must travel via the river.  At the upstream end of the park is the Summersville Dam, the only area of the park accessible by vehicle.

Supporting paragraphs: Willard Beach Fort Gorges
Answer: Fort Gorges