Ah, now that I look at the map... The Lampasas River flowed near Camp Tahuaya, between Salado and Belton. It is the Leon River, flowing out from the Belton Lake, that went by that swimming pool.
This link is on the former Terraserver topographic map site, now Microsoft Maps Research. The small blue rectangle next to the Leon, east side of Belton, is the location of the swimming pool. I remember some of us going up by the Pumping Gauge Station and there was a small concrete dam there.http://msrmaps.com/image.aspx?T=2&S=12&Z=14&X=81...
The 9-hole miniature golf course was there in about 1963. I don't think it lasted long. Not much in the way of shade.
I took swimming lessons at the Natitorium around 1952. Sorry, I felt like I was swimming in ice water. I have somewhere some photos of the pool about 1966. It was the off season and was empty of water.
I see the Belton drive-In Movie Theater is no longer shown on the topograhic map, nor are the ones in Temple still shown. I remember the Tem-Bel Drive-In about at Midway, but not the names of the others.