Wide angle and macro are the two most common photography techniques under water. The reason is that light travelling through water is affecting image quality and both these techniques keep the camera close to the subject. Most of the crisp, clear and colorful images you see are usually one of these two techniques.
Selecting a lens
Wide angles for under water starts around 20mm and go down to about 12mm, then it goes over to fisheyes. The wide angles are narrower and give images with less spherical distortion. Fisheye makes more spherical images and tend to be sharper towards the corners of the frame. Bare in mind that light is broken when it passes from water into the air-filled dome. This makes it narrower. A 15mm will be more like a 20mm on land, I do not like to much distortion and go with 14 and 15mm,
It is believed that the strobes on wide angle are supposed to be as far out to the side as possible. This is not always the case. Put a wide diffuser on the strobes and experiment a little. When the subject is close it is often better to bring in the strobes too.
Shooting wide angle you want to balance between the ambient light and your strobes. I do this simple. When I reach target depth I tilt the camera slightly upward and measure the light in the scene. Then I go up 2-4 aperture stops, put my flashes on a low value and shoot a couple of exposures. Then it is only small adjustments to be done when you start shooting. When you go closer you turn the flashes down and opposite when you move away. I usually shoot manual because I want to control everything. If you want a simpler solution you put your camera in a program mode and adjust down a few stops so you slightly underexpose.
Shooting a wide angle you will have sufficient depth of field at aperture from 11-16. If you are deep you then need to compensate with ISO and increase the strobes.
Test shoot on land and get familiar with your options so you do not use valuable bottom time testing.