An underwater light is any device providing illumination beneath the water. NauticExpo offers a great variety of underwater lights: LED, xenon, for yachts, etc.
Underwater illumination systems include those for shallow water, such as through-hull and pier lighting. ROV lighting is designed for deep-water use.
Underwater lights differ according to application. ROV systems can withstand high pressure, while through-hull lighting found on some yachts only work at shallow depths.
Choice will depend primarily on intended use.