What is Marina/Dock Lighting?
Mariana/Dock Lighting is underwater lighting that illuminates the surrounding water and the marine life in it.  Fish are attracted to the lighting.
 
Why do people use Underwater Green Lights?
 Most people choose green lighting for their docks due to the fact that green light travels through the water better than many other colors, revealing both the abundant bait fish and the hungry thieves that move in to feast on them