A thru-hull fitting assembly is connected to the forward end of a hollow lamp housing for mounting to a hole in the hull of a vessel in a water-tight fashion. An HID or other lamp is mounted in the lamp housing and is surrounded by a reflector which may have an outer elliptical section and an inner parabolic section. A protective transparent window extends across the forward end of the lamp housing and is sealed thereto. The window may be made of sapphire to provide improved heat dissipation and to resist scratching during hull cleaning and breakage due to thermal shock and wave slap. A circuit may be connected to the lamp to provide over-heat protection, leak detection, as well as fault and power status indicators. Alternate embodiments utilize a solid light pipe or a hollow reflective tube to convey light from the lamp to the protective window.