I installed the Abyss S-600B's a few years back and absolutely love them! Turns heads and get great reviews where ever I go and so awesome to swim in at night! Check them out.
http://www.abysslite.com/underwater-lights.php
Check out some pics of the lights in action. The lake that these photos were taken at is pretty murky. In clear water, the lights flood out and around the stern for about 20ft. During night cruises, the entire wake is lit up as well.
Fairly simple install and well worth the price.
Sorry, couldn't get the uploader to work anymore.