I wrote a blog on my website with a few simple tips that hopefully will help any underwater video shooters out there. I learnt them right at the start of my career, so they are mostly aimed at newbies I guess, but I still find them useful today, after 17 years of filming underwater.
Learning to be aware of the position of the sun and trying to keep it behind you (or shoot in overcast/low sun conditions) does indeed make a huge difference. This can sometimes be tricky while also trying to get below your subject and isolate it against the water column as a background, depending on the topography of the dive site.
But no matter how powerful your video lights are, they're not going to help you much if you're trying to shoot straight into the sun.