This is a Gray Angelfish . Photo by Rod 07 Feb 04 in about 30 feet water. 
Location was The Elbow, Key Largo 
Pomacanthus arcuatus
       
   
   grang07.jpg                                         
 greyang32c.jpg         
                     
    (greya49.jpg)
 
  I reduced picture size so they would be visible on your screen. Just 
click on thumbnail for 6 x 4 picture, and name for 10 x 8 full size picture 
or more info 
greya49.jpg is from North-North Dry Rocks.............
greyang32c.jpg is a Gray Angelfish over the Benwood 
Wreck 
More pictures at 
Audubon Field Guide; page 549; plate 325; 
Reef Fish ID 3rd ed.; page 24-25 plate 25; 
Size: 10-18 inches; max 24 inches 
Depth: 10-60 feet