Within Moraine State Park, Lake Arthur 40°57′45″N 80°07′19″W is open for year round recreational enjoyment. It is the home of the Lake Arthur Sailing Club and the Regatta at Lake Arthur. In addition to sailing the lake is a popular fishing destination and it has two swimming beaches. Osprey and Bald Eagles have made nests in the tree tops along the Lake Arthur since the mid-1990s.
All boats up to 20 horsepower (15 kW) are permitted on the waters of Lake Arthur with certain restrictions in the "game propagation area". Sailing is an especially popular activity. Races and regattas are held at various times over the course of the summers. Sailboats, rowboats, kayaks, motorboats, canoes, and pontoon boats are available to rent in the Crescent Bay Area. There are two fueling points for power boats. These marinas also have docking facilities and sell boating supplies and groceries. All boats must have a current registration from any state or a launch permit from the Pennsylvania Fish and Boat Commission. The lake is open to ice boating during the winter months. Ice boats must display a state park launch permit.
The Moraine Preservation Society operates a Passenger boat available for tours and dinner cruises of Lake Arthur. The organization also operates a gift shop and has been responsible for re-establishing many bird species, environmental education programs and attaining additional land for the park.
A section of the lake near Barber Point is very popular for windsurfing. This is due to the higher than normal winds and relatively low boat traffic. All windsurfers are required to have a launch permit. Windsurfing lessons are available.
Lake Arthur is a warm water fishery. The native fish species are largemouth bass, bluegill, black crappie and channel catfish. The fish commission stocks a population of walleye, muskellunge, and striped bass. All anglers are expected to follow the rules and regulations of the Pennsylvania Fish and Boat Commission. Lake Arthur is open during the winter months for ice fishing.
Two beaches at Moraine State Park are open for swimming daily, Memorial Day weekend through Labor Day weekend from 11:00am until 7:00pm. Pleasant Valley Beach on the south shore is a 1,200 foot (365 m) grass and sand beach. It has a paved path that leads into the water and a sand volleyball court is nearby. Lakeview Beach on the north shore is a 550 feet (170 m) long sand beach. Each beach has a bathhouse with showers and a snack stand.