There are a few reefs that run north to south for many many miles in that area of south Florida in a few different depths. The closest to shore is in about 10 or 15' of water. That one is fairly low in relief & there is not much on it. The first really big one is in 90'-120' of water & seems to be the one that is most heavily used by the cattle boats. There is another out around 250' that is mostly used by fishermen, but some tech divers use it as well. There are also patch reefs in the area that are in varying depths. A google earth view shows the locations of the major reefs.
There are a couple of rows of moorings in front of the breakers. They are more or less around 30 feet deep. They have small low patch reefs all around them. As a previous poster stated, they were put there so that local boaters would not drop anchors on the reefs. The area is commonly used for snorkeling. It is also used for scuba, sun bathing, hanging out, grilling, drinking, & fishing.
If you tie up to those moorings, it's a good idea to dive on them & check the hardware. When I found some to have shackles that were worn more than 80% of the way through, I had a hard time finding the proper authorities to report that to. The agency that put them in said that they were not responsible for maintenance. A few months later, I did find a new shackle on a mooring that previously had a bad one.
