How to create visible reflections in shallow water? Assumption: The only lights I have are candle, table lamp, and sunlight.
What would I need to create visible reflection of an object in the shallow water contained in a 5 liter bucket? Is it even possible anyhow?
What kind of light out of the three will maximize the visibility of the reflection in this case?
 A: If the problem with shallow water is that you see the walls and the bottom instead of only the reflection, I would just use a black bucket. Or somehow make bucket's inners black.
Moreover a bucket is a bit unpractical in this case, just a really black tray with water should suffice.
Another option is to make water black itself, like using coffee.
UPD All three light sources should behave identically in terms of reflection provided the water/tray is really black. However in real world the brighter the light the darker color is required. I just advise you to try it yourself.
There is another matter you might be interested in. The portion of light reflected greatly depends on the incident angle. If the light goes almost parallel to the surface it will be reflected almost completely. So if you are trying to imitate a reflection of houses or trees on a river bank (tangent light) you'll get brighter reflection than if you are looking straight down into the bucket.

The logic is quite simple. When the light hits the water most of it passes through the surface, the smaller part is reflected. In deep water the light that passed through eventually dissipates and does not return back. All you see in that case is the reflected light.
In shallow water the light hits the bottom and bounces back riving with one that reflected.
So all you need to make reflections visible is to eliminate the light that comes back from the bottom. Either paint the bottom black or make water black.
However I don't think it is how I was reasoning. I've just remembered an analogous situation with windows. When you are indoors at night with room light on your windows are essentially mirrors.
A: For a "visible" (clean/clear) reflection we need to optimize the contrast of our image, and minimize the amount of visual "noise".
Given a specific image, a surface with higher specular reflectivity will reflect more of the light without adding noise.
A surface can also have diffuse reflectivity, which will increase total reflectivity, but add noise, (blur the reflected image).
The smoother the water surface, the higher its specular reflectivity and lower diffuse reflectivity.
(Practically that means shielding it from vibration and wind)
Another parameter is the water's total reflectivity, and as @Yrogirg had already mentioned, " The portion of light reflected greatly depends on the incident angle ...", so maximizing the water's reflectivity in relation to our view point means getting as close to parallel to the water's surface as possible.
This will also reduce, partially or completely, the portion of light that travels inside the container on its way to our view point, which means less noise from that source.
Visual noise can come from 4 sources:

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*diffuse reflectivity, (which was covered above).

*Reflections from within our shallow water container, (partially covered).

*Obstruction, refraction, and/or diffusion of the light, as it travels through the air between our image source and our view point.

*Optics glare, or "light pollution".

Source (2) was mentioned by @Yrogirg, with possible solutions: reduction of reflection, (e.g. by painting the inside of our container), and/or noise-diffusion, (e.g. by adding colorant to the water itself).
Source (3) is mostly obvious: remove objects from the path, and keep the air as dust-free as possible, but also make sure you cover less obvious details like container edges, water surface curvature, (due to surface tension), etc...
Source (4) can be prevented almost completely by using good quality "glare reducing" optics, and by shielding them.
There are two other parameters which affect any "visible reflection", but have less to do with physics (or reflection), they are:

*

*The quality and contrast of our original image, and...

*The viewer, (practically speaking, our sensors, and the way they capture and interpret light).

The topic of lighting on our reflected object and its surroundings, (foreground and background), is more of a practical "photography", "art", or "image rendering" related question then a "physics" one.
"Sensors" are (imho) completely outside the scope of this forum.
