I have not dove in miami but have a few friends that went down there which had a similar experience to yours. sounded very hectic and unorganized. There are pleanty of boats that go out close to you which have great diving without the crowded experience, none I know of in miami tho. Come a bit north to Ft. Lauderdale and there are pleanty of boats that go out that I have never had an overcrowding issue, even on a full boat there was still room to move about. And if you go a little farther north to pompano like some have said you will find many nice reefs and wrecks and most the time I have been out there have been empty seats on some of the boats and always pleanty of room. And overcrowded boat = not as much fun