Gray's Lake is an immensely popular park, just south of downtown. People of all ages come here to play, jog, cycle, boat, and swim. Des Moines Parks & Rec frequently hosts Saturday morning yoga at this park (although it rotates some weeks).
The northern most entrance to the park leads to a parking lot by the old silos, which is a good spot to park for the playground and beach access.
From the playground, we strolled along the Kruidenier Trail, which makes roughly a 2 mile loop
around the lake and connects with the Meredith Trail on the south end of the park. We walked around the southern end of the lake and stopped at the concession stand. The concession stand is where you can rent boats.
Some pretty views of the lake and downtown can be seen.
You can see some of the paddle boats and canoes they rent out. You can actually register to take a canoe or sailing course as well. Here are the link to the community courses where you can find more information.
We didn't spend time at the beach this visit, but there is beach access on the north side of the lake, near the playground. Here are pictures from a couple years ago when we played at the edge of the lake.
On the map below, I tried to mark the areas I discussed above. The spot I have marked for parking isn't the only parking at Gray's Lake. There's a parking lot near the concession stand and another lot right at the north entrance.