Before planning anything at Cowan Lake, know that the lake is being drained. ODNR opens the dam valve on November 1 to begin rehabilitation of the Cowan Lake dam, dropping the water roughly two feet per day until it sits about 13.5 feet below summer pool. Construction runs from early 2027 into spring 2028, the lake is expected to stay drawn down through the entire 2027 season, and ODNR is targeting summer 2028 for a return to normal levels. ODNR says the lake stays open for fishing and kayaking at your own risk until there is no longer enough water and the boat ramps are inaccessible. The public beach is not posted as closed, but a drop of that size will leave the waterline a long way out from the sand, so treat 2027 as a lost season for swimming here and call the park office before driving out.

In a normal year the swimming is at a 1,000-foot public beach on the south lake shore, near the Dance Pavilion. There is a changing house and there are restrooms. Swimming is allowed during daylight hours only, and only inside the designated area marked by buoys. Nobody is watching the water. Ohio State Parks do not put lifeguards on their beaches, so every swim is at your own risk, and ODNR asks visitors to keep an eye on children and inexperienced swimmers. The beach is Carry In, Carry Out with no trash cans, so bring a bag. A separate boat swim area and a boat camp sit in the northern part of the lake, and the campground has its own beach, which the Ohio Department of Health monitors as a public-access site in its own right.

There is no fee to enter and no fee to use the beach. ODNR charges no entrance fee at Ohio state parks, and its own swimming page states that state park beaches are open year-round and are always free. What ODNR does charge for is overnight and dock use: the campground's 254 sites and 21 cabins, and the 48 seasonal docks, all booked through the state reservation line on 866-644-6727. The marina concession charged separately for boat and paddlecraft rentals, and that arrangement is ending. The Taylor family had run the marina under state contract since 1985 and will not have its agreement renewed, because the building is being demolished and rebuilt with new state-owned docks, a retaining wall and municipal water.

Cowan Lake's water quality problem is bacteria, not algae. The Ohio Department of Health monitors two beaches here, Cowan Lake Main and Cowan Lake Camp, and has posted fifteen advisories between 2011 and 2025. Every one of them was for high bacteria levels, typically after rain, and most lasted somewhere between two and nine days. The most recent went up at both beaches on July 23, 2025 and cleared on July 28. In that whole record there is not a single harmful algal bloom advisory, and Cowan Lake does not appear on Ohio's public HAB advisory site. Check BeachGuard before you go between Memorial Day and Labor Day, and give the lake a day or two after a heavy storm.

The lake was impounded in 1950 on Cowan Creek, so this is a reservoir rather than a natural lake, whatever you may read elsewhere. Boats are capped at 10 horsepower. That single rule is why sailing dinghies and kayaks dominate the surface, and why the Cowan Lake Sailing Association has been racing Snipes here for decades. Three ramps and an accessible kayak launch ring the shoreline, and the campground commissary rents kayaks and paddleboards seasonally, first come first served. On land there are more than eight miles of hiking trails, including Emerald Woods at 1.8 miles, the 2.6-mile Spillway trail on the south side, and short campground loops such as Beechnut and Lakeview. An 18-hole disc golf course sits near the Dance Pavilion and the public beach, and there is a nature center and a half-mile Storybook Trail. Park hours are 6am to 11pm. The park office number is (937) 382-1096.