"CRUISING THE DEEP"

I don't know a lot about underwater photography but in this photo, it seems you need to be a bit closer. Also, your flash must be in line with your lens, causing all that backscatter (all that crud floating in the water to light up). So, get a bit closer and move your strobe. Also, have your daughter secure her octopus (alternate air source) to the triangle formed by her mouth and the lower corners of her ribcage. :)

Happy shooting (and diving)

David.

Also, I'm sure you get better photos automatically in exotic places - you better go check some out!!

Generally we want to see the subjects face. But if it is a black mask, and you have a single and not very powerful strobe, you may not be able to light up the face.

Besides that you normally need to shoot upwards instead of downwards. This means you are deeper than your subject, shooting upwards at an angle. The lighter background then outlines your subject nicely.

You really need to angle your strobe to prevent back scatter. Direct frontal strobes will illuminate all the water particles to the camera. In your case you will need longer extension arms. If they are detachable, then just hand hold and stick it out more.

All these are just general guidelines.