There are no walls in the sense of Cozumel or Caymans. There are some drop offs, like part of deep molasses but not what I would call a wall dive.
There are manatees around the Miami area especially in the rivers and bays. But I am unaware of any specific manatee trips outside of those up in the Crystal river area which is not Miami. I have seen them in the harbor at mile post 100 at Key Largo (where ocean divers and rainbow run from) and up around Sebastian inlet.
