There a few different manufacturers and choices for lighting, but hands down the best lights I've seen are the ones I ended up with. The company is Deep Sea Lights, located in San Diego and their background is lighting for underwater submersibles, so they build their stuff like a tank.
There are a number of different choices in lighting, as well as voltage. You can install 12 V systems thru 120V.
On the 120V side, the cheaper underwater light set-ups range from modified pool light bulbs and housings to high end HID bulbs, mounted in Titanium housings with Sapphire crystals for lenses.
I went with the Deep Sea set-up, which was the high end HID bulbs and the Titanium housings and couldn't be more pleased. While any underwater lighting at night is nice, you can definitely see the difference in results.
Cost wise, they ran about $2200 a piece, but at least I didn't do an install and wish I had something later.... the whole family has been more than pleased with the results.
You can checkout their lights at
www.deepsea.com or
www.deepsee.com
There are a few shots of my boat in the pic section. I don't have an affiliation, only lots of satisfaction from a good product.
If you call ask for Erik or John and tell them I said hi.
Best regards, Bill on Play-N Hookey