i have been asking about diving spots in the south near boca chica for years. Nobody ever responds.
There's a long continuous reef with just one sand channel cutting through going east from the megaport. I just checked the coordinates on my google earth the reef is 2.94 km. I've done the whole thing, I know. East from the eastern end there are some smaller mountains before another long reef. The small mountains are very hard to find, without a sonar and gps forget it. I have never seen any other divers there except my buddies. Even those "in the know" haven't been there when they finally get there and see. I know that as well (arrogant today). Now, there's no free lunch, the top of these reefs are between 70 ft and 100 ft, and on the south side these are going down to 150 ft++. Start practising.
I have heard there are a couple of nice diving spots in guyacannes...very close to BC. But i have yet to find them.
Same, fantastic reef. Further from the coast and a little deeper. No diveshops bring your own stuff.
The point I'm trying to make here is there are plenty of reefs, but the shallow reefs are cleaned up, destroyed. Some of the deeper reefs are really good, but without preparation it's not possible to do a safe dive on them. Keep practising.
And BTW I'm not a diving instructor.