Cocoa Beach/Port Canaveral Diving is WAY off the coast, like 20 + miles out to Pelican Flats. Vis is generally poor, but big lobsters can be found out there. Depth is 90-100 feet.
Sebastian Inlet - about 1 hr to the south end of the county, has 4 different depths. A 20 to 30' beach dive (must have small surf) can be done. Vis ranges from 0' to 10' maybe, make sure you have an incoming tide, as the river water makes everything close to the inlet resemble coffee with a dab of cream - no vis. Watch for the sea urchins too, you get a lot of surge on the shallow stuff and if you're not careful, you hands will be pricked by them as you try to keep off the ledge. Also there's 45' and 60' and 90' ledges. The 90' stuff is very far out, like Pelican Flats. Shallower 45' and 60' sites can get good vis, but need a boat.