Close focus wide angle (CFWA) is one of the "oldest tricks in the book" for many professional photographers, and has graced many magazine covers. The technique takes advantage of 2 inherent characteristics of super wide lenses: close focusing capabilities and great depth of field.
Close focus wide angle can provide a really unique perspective on small, macro subjects. It gives some dimensions and a sense of scale to small creatures like nudibranch and lizardfish that are typically shown to be filling up the entire frame.
Close focus wide angle is also great for diver silhouettes if you have a dive buddy that's willing to keep an eye on what you're shooting and position themselves within your frame.
All waters, with particular emphasis in high visibility waters where secondary subjects and backgrounds can be far away from the primary subject.
DSLR + Mirrorless
ISO: 200 to 400
Mode: M Manual
Aperture: f/8 to f/16
Shutter Speed: 1/125
Point + Shoot
ISO: 200 to 400
Mode: M Manual or Av Aperture Priority
Aperture: f/8 (or smallest available)
Shutter Speed: 1/125 to 1/200
A wide angle or fisheye lens with a dome port is essential. Shoot at an upward camera angle with the dome very close to the object: no more than 1-2' away at most. Get close to your subject but stay off off the reef! With a very wide angle lens, this will often include the sun and surface in your image.
Bring your strobes in very close to the sides of your dome to light the foreground subject. The background should be properly exposed based on the aperture and shutter speed you've chosen.