I am running these on my 21V I ordered them from amazon I included the link below.
They are only 18 watts and only about 8" wide and I use my switch that controlled my Roswell lights to control them.
We have wakeboard at night with them and decent for wakeboarding. (I could spot my landing.)
and for surfing we just turn them to the back corners (sort of more to the side of the boat. If you shine them right at the rider they get a little bright.
back of boat.jpg
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1