Chestnut Run Swim Beach is the designated swimming area on Shenango River Lake, a U.S. Army Corps of Engineers flood control reservoir in Pymatuning Township, Mercer County, in far western Pennsylvania. The Corps' Pittsburgh District runs the lake, which backs up the Shenango River for about 11 miles above the Shenango Dam at Sharpsville and reaches into Ohio. The beach sits on a small cove on the lake's north side, below a wooded slope with a picnic pavilion and a paved parking lot. Mercer County leased the beach from the Corps from 1978 until 2008, when the county ended its lifeguarded program because of low attendance. The Corps kept the area open afterward as an unguarded beach.

The access road is Chestnut Run, a short paved lane that leaves Saranac Drive (PA Route 846). The Corps gives the address as 500 Saranac Drive, Transfer, PA, though some event listings use 5500 Saranac Drive. Parking is free in the lot directly above the sand, and it is a short walk down to the water. The village of Transfer is about 2 miles to the northeast, and Sharpsville and the dam are about 4 miles south.

The beach is a strip of sand roughly 150 yards long on the north shore of the cove, facing south over open water. The lake is a dammed river valley rather than a natural lake, and the Corps describes it as shallow, with no current to speak of in summer. There is no lifeguard on duty, which the Corps states plainly on its Recreation.gov listing, so swim with a partner and keep children within arm's reach. Pennsylvania law requires children under 13 to wear a life jacket on boats, and a life jacket is a sensible idea for weak swimmers here too.

There is no admission charge for the beach. The Corps does not post a day-use or beach fee for Chestnut Run on Recreation.gov, where the only charge in this area is $51 to reserve the picnic pavilion. The beach is open year-round, but the restrooms are seasonal and are typically open from late May into early September. The pavilion has no electricity; generators are allowed.

The main thing to plan around is water level. The Corps notes that the lake is shallow and generally drops through the summer, especially after the Fourth of July, depending on rainfall. In a dry August the water line can pull back from the sand and leave a muddy margin. After heavy rain the reservoir holds back floodwater, so the level can rise fast and carry floating debris onto the beach. Shallow, warm reservoirs like this one can also grow blue-green algae in late summer. If the water looks green, scummy or like spilled paint, stay out and keep dogs out of it, and check with the lake office at (724) 962-7746 for any posted advisory.

Outside swim season the beach still gets used. Each January the Corps and the Shenango River Watchers hold Eagle Fest at Chestnut Run, since bald eagles gather at the open water near here once the rest of the lake freezes; visitors have spotted more than 90 in a single day. The beach also works as a put-in for kayaks and canoes heading out onto the quiet north end of the lake. The Corps' Shenango Recreation Area campground is about 3 miles away by road for overnight stays, and the Bayview off-road vehicle trails are just south of the cove.