It’s crazy hot, and swimming feels good.
Pictured above is a small beach on the north shore of Lake Lewisville. It’s not amazing, but you can bike there from Denton.
I sought destinations via Denton’s MKT rail trail, and in this weather, a swim sounded inarguably good. My route used the rail trail for almost the whole way, which was nice and stress free: no cars to worry about. There are some good, long stretches where you can ride without feeling rushed.
Swisher is car-dominated, and there’s no sidewalk, so I rode that short leg of it anyways. If you look at an area map, you can cut through a neighborhood to skip that Swisher part, taking Dobbs to Shady Shores rd. I rode into West Lake park, and the gate staff pointed me to the boat ramp-y area to the left. Meh. It was not really a swimming area. Just south of the park, there’s a beachhead parking lot on your left.
If you get hungry on the way there or back, the El Centro market has a Taqueria inside, you can get your breakfast taco on.
Bike Denton 
Guess where I’ll be this weekend.
Ridiculous question, but is the rail trail a mountain bike trail?
It’s a paved, 8′ wide path from downtown Denton to Swisher road. I think it’s roughly 9 miles long, and it works well for all types of bikes. If you like mountain biking, the Corinth singletrack has a trailhead that intersects with the rail trail, so that’s a nice (woodsy) deviation.