My first real photo lesson was underwater and has become my specialty for 24 years.
Get close to your subject, then get closer! with the exception of shooting natural light, getting close eliminates the amount of water you shoot through making an image clear.
I believe the camera, while underwater is an extension of your body, use it to gain your best buoyancy or balance underwater in order to get better pictures.
Practice holding your camera in different positions while underwater and perfect your buoyancy, making you more