An anti-fouling lighting system is used for protecting a surface (16) against biofouling while the surface (16) is submerged in water. A non-contact water sensor (60) is used for sensing water thereby to detect whether or not a light source arrangement (26), or a portion of the light source arrangement (26), is submerged in water. The light source arrangement (26), or the portion of the light source arrangement (26), is controlled in dependence on the water sensor (60) output.