...never been to Lake Waco, but the Dallas Ft Worth area has a few decent sites.
1) Clear Springs Scuba Park (Terrell/TX), maybe 30 miles due east of Dallas. In the summer the thermocline was around 25--30 ft, and the best visibility I saw was my last spring/early summer trip.......visibility was pretty good, one could clearly see the surface while standing on the 25 ft. deep platforms.
LOTS of fish!!! Max depth 60 ft.
2) Athens Scuba Park (60 miles southeast of Dallas)......doesnt have any fish ) Max depth 30 ft or so. Visibility not as good as Clear Springs, although sometimes it can be pretty decent.....being a smaller/shallower lake than Clear Springs, it's a lot easier for student divers to stir up the bottom, so visibility depends greatly on the # of divers there.
3) Possum Kingdom......a bit murky, but if you go when it's not stirred up by student divers, I've seen OK visibility of maybe 20 ft......a bit murky, but you can make things out.......but sometimes the shallows where the students congregate can generate visibility of inches....so you'll have to dive off the cliff, which starts @ about 15 ft, to get any visibility on those days.
4) Aquarena Springs (San Marcos).....you can dive there for free, with free air fills too and the visibility is unmatched for fresh water diving.......but you have to graduate from their 'scientific diving class to get permission to dive there...which takes 2 days and costs $200.......I 'graduated ' from there in Sept 2002.......it's a fun dive....max depth is maybe 30 ft......temp is 72 degrees year round, as it's spring fed.
Karl