It is called Liter Light which is actually a 1-liter plastic bottle of Coke. Half-filled with water and some bleach, it can project the sunlight and serve as lighting for indoor during the day. The Liter Light is installed on the roof of a house that needed lighting during daytime. This is very useful in crowded urban areas. It’s just like having a free light, no electricity required.
Light water technically speaking is a coolant. It cools off the machine or the engine. I think what you mean is a bottled of water that emits light. It is invented by a Brazilian mechanic Alfredo Moser who came up with a light-bulb made of plastic bottles filled with water and a pinch of bleach. This invention came out sometime in 2002. Several underdeveloped countries are already using this Moser lamp. Moser with his lighted water-bulb invention. Image by BBC news
I am wondering how much light this would actually give off? I guess it would do in a pinch if you needed a light. However, i doubt it would work in any kind of long term way. Sometimes simple solutions can be the best ones it seems. I would be interested in trying something like this sometime.
It is indeed cheap and readily available "light bulb." The question is how much light is actually emitted from such a bottle. Why during the day time? Does it depend on sunlight? More of a solar-bleach panel. Nevertheless, it can help especially those who read in low lights.
I've used the liter and it does help to light the house. It doesn't emit alot of light but it's enough since we don't need too much light during the day and using electricity is expensive. You can alternatively use translucent iron sheets on your roof. They allow light to penetrate into the house and also regulate the heat.