Driving from Philadelphia to a lake worth swimming in

Grenloch Lake in Gloucester County, New Jersey. Its nutrient and algae readings are among the most favourable within reach, and the drive is 24 min, or 15.5 road miles. The closest lake of any kind with readings on record is Newton Lake at 14 min.

10 min each way. Newton Lake is 14 min out; Grenloch Lake, with the more favourable readings, is 24 min out.

9 of the 40 lakes here have a public access point on the record, and the closest is Lake Luxembourg, 45 min away. The rest of the table shows "Not recorded" where no access point was documented, which is not the same as no access — check with the managing agency before you trailer a boat.

By road, from downtown Philadelphia to the nearest public road at each lake, over the OpenStreetMap road network. They are free-flow times: no traffic, no time of day, no stops. Treat them as the floor, and add for rush hour and for the last stretch to the water.

No. The readings summarise years of phosphorus, nitrogen, algae and turbidity measurements; they describe the lake, not this afternoon. A beach closure, a bloom, or a heavy rain can change conditions overnight. Whether a lake is safe to swim in is a call for the state water agency and the county health department: check the lake's own page for its measurement record, and check the managing agency for current advisories before you get in.