Hardly anyone can answer this question confidently. However, I will try to explain my point of view.
They all are different, and all water bodies are different, but I would say that everywhere fish will prefer those depths that are convenient for them and that will meet all the requirements.
Therefore, the depth of water in the place where carp will be will depend on the season and weather conditions at this time.
Carp will always look for a place that will provide him with enough food, heat, safety and oxygen. I think that you will agree with my opinion that if one of these requirements is not met depending on the season or weather conditions, the carp will necessarily look for a place where it will be achieved.
It explains the migration of carp during the summer. The concentration of oxygen in the water at that time in many lakes is small, mainly because of the increase in plant growth and the number of different organisms that will consume oxygen. The water near the shore, where the wind blows, will contain more oxygen than other areas of the reservoir. Therefore, carp will probably be on the windward coast. It also means that the carp will often be in the upper layers of water or at a shallow depth because there will be more oxygen. Even at this time in such places, there is food, which is also essential.
In winter and other cold months, I believe that carp do not need to follow the winds. At that time, the amount of oxygen in most lakes is vast, and if there is enough food in the lake, then the carp does not have any need to follow to the windward shore. In fact, in winter, carp needs warmth, and it will find it at greater depths and away from any cold winds.
I inclined to believe that carp will be at some depth, most of all to find more heat for yourself. If the weather changes and becomes more cooling, the fish will look for warm water in deeper layers.
Although, this does not necessarily mean that the thicker it is, the warmer water it will find. In some lakes, warmer water is in the middle layers, and they will be the ideal depths for carp for a particular time of the year.
The greatest depth is not always the warmest in the cold months, because freezing water always lowers to the base of
the reservoir. Moreover, deeper parts of the tank can become the coldest in individual seasons. It can take place in the warmer months when it is cold, or there is freezing rain. Cold rainwater begins to sink to the base of the reservoir, and carp prefer the middle depths of the lake, where the water will be a little warmer.
While the water does not cool down to four degrees, it will rise to the upper layers of the reservoir. When the winter comes, and it becomes icy, the lakes will hide under the ice edge, then everything will change, and the deepest places in the pond become the warmest. Then carp will most likely lie down to the bottom and will probably eat only at this depth most of the time.
In a small number of very deep European reservoirs, сarp may prefer to eat only on small coastal depths. There is enough heat and light so that seaweeds and other aquatic organisms can develop here; carp can find enough food and excitement at certain times of the year. Also, carp may prefer to eat a little deeper, where a lot of food accumulates. However, it is known that changing the pressure can change the natural nutritional habits of carp. Therefore, if the pressure sharply begins to fall, the carp will most likely go to broader sections of the reservoir, eating other available natural food at great depths.
Virtually, it’s probably a good idea to fish carp in areas where there are sharp changes in depth, especially in winter. Any changes in the temperature of the water can cause the carp to stay at the bottom, or to rise higher into other parts of the reservoir.
In such a place, you should drop your baits both to the shallows and to the depths to be able to catch the fish that will move from the shallows to the depth or vice versa, even due to insignificant changes in the weather during the day.
Regardless of how deep you are going to catch carp, I think it’s important to remember that carp will eat absolutely at any depth if he is hungry enough. Make the carp want to eat and compete for every piece of food, and they will eat your meal at any depth and anywhere!