I can't help you on shore diving off Miami Beach. The water always looked green and was covered in an oily sheen from all the sunbathers and who-knows-what. Dade county advertisers itself as the artificial reef capital with 8,000 feet of wrecks and structures.
In fact, I'm the last person to ask about shore diving since I refuse to do it anymore. Too many years of doing it for a living.
RJ has a dive boat right at the Marina on Alton Road - you can see it crossing east on 395 just before you land on 5th Street. That's your best bet for diving there. If you like the operation and become a regular, you should be able to get a good rate from him. In Hawaii, we always took care of regular repeat customers. They required no pampering and helped out a lot.
South Beach Divers on Washington wasn't much of a dive shop, and as much as I tried to like Tarpoon Lagoon also at the Alton Road Marina like RJ, that wasn't a good fit either although Valerie the owner is very nice.
Make sure you eat at Puerto Sagua over on Collins and 7th. It's a great place especially once they realize that you live there. I can't believe it's still there with all the upgrading going on.
I never get down to South Beach anymore - as much as I loved Miami Beach, I loathed the rest of the county. I missed Pizza Rustico on Washington and 9th until they opened a branch on Oakland Park and A1A.
I bypassed all of Broward county when I made the permanent move here and wound up happily ensconced at the Club Tom.
As much as I miss living in South Beach, I sure do not miss the parking nightmare there, especially on weekends. And the noise. And the dirt. And the weekend partyers. I never hear gunfire anymore on Friday and Saturday nights.
http://www.rjdiving.com/