This is what is posted on the Missouri Department of Conservation. I have also called and spoke with several people there to make sure they are legal. from what I was told and what is stated in the laws they are legal when fishing by pole and line.
Use of Lights
As an aid to fishing methods, an artificial light may be used only above the water surface.
However, while fishing by pole and line only, underwater lights may be used to attract fish.
New! Underwater lights also may be used when bow fishing on lakes, ponds and other impoundments.
I would sure like some more input if I'm wrong (or the gentle men at MDOC)
Thanks for all the feed back!