To test your side view sonar the bridge at 29 33.93N 95 3.251W ( taylor lake under Nasa Rd 1 ) ( pinkies )
you can see the bridge supports and all the pilings on the way out, I was very impressed , I had not found
anything to see before this point.
Testing your sonar you can cross any of the major channels and get a quick dip, for example the ship channel is around 50 ft and the surrounding area around 10 ft.

I have yet to find any other structure that I went looking for.
Please post up your favorite test points that are basically safe .