Most diving in Antigua is out at Sandy Island and Cades Reef, there are a few spots in the south. Even in the winter season when its at it's driest the sand nature of Antigua means that visibility is not as good as say Bonaire which is noted for its vis.
Check out the dive sites for Antigua and Barbuda
Cades Reef viewed from the air courtesy of Jolly Dive.
Barbuda Diving Link - http://barbudaful.net/things-to-do-see/watersports/diving.html