If you're truly having issues with Lightning I'd suggest finding a nice cozy mahogany drop off and a bottle of you favorite rum and sit out the storm. I'd had some very memorable dives under ongoing Lightning storms but it's not for everybody. If you really meant lighting (as in strobes) I'd council to get yourself a copy of The Underwater Photographer by Martin Edge, still the bible for strobe positions and basic skills to learn. There are also some great websites that have some really good information. The Underwater Photography Guide has some good examples on their website as one example. I've found no matter how much book learning you can get it's still necessary to get in the pool and practice. If none of that advice helps there is always the reminder to shoot up.
In the image you attached I would think about pointing the strobes higher so the bottom of the light cones just cross at the little ray. No reason the light the bottom. The bright bottom also makes the shadows more prominent. Might look something like this;
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