When you read my post about selection of lenses you see that there is reasons for getting close to your subjects under water. Sometimes you have to many particles in the water to get decent wide shots. Then it is all about getting close and use the lights smart.
When you jump into the water you sometimes get surprised of how low the horizontal visibility really is. You have seen the crystal clear water from above and put on your widest lens. Well you are stuck and have to go with it and it usually turns out better than you think. This is when you want your flashes out wide and try to think about how not to make it reflect too much particles. Do all the things you regularly do. Tilt camera upwards, set aperture to more natural light than you normally would and set your flashes low. The natural light comes from above and will backlight the particles. This will make your images better looking than you think under the circumstance. Tilt the flashes wide and more in from the sides and bottom.
Here is an image from first dive on Antigua yeterday. It was a rough ride out to the dive site. 6-8 feet of waves that we still could feel 40 feet down. Then visibility is usually quite low.
The visibility was worst in the surface area, so I shot most of the images deeper. Got really close to the subjects. Closer than usual. Get more distortion this way. Look what I got. The particles does not show as much. This is shot with a 15mm and as you see it is a little more difficult to get close to the animals. The swelling throwing you from side to side made it even worse.
Then on the second dive you know you got to switch to macro. Does not matter if there is mantas and mating tiger sharks, your will not get decent pictures anyway. But with macro in this low visibility you get things like this.