An adult human being consists of 65% water on average. Many people can swim and can even lie on the water without making unnecessary movements. At the same time, divers usually search for the body of a recently drowned person, since it goes under water. But the corpses of drowned people often float up and are washed ashore. Why then do some human remains remain at depth? And do dead bodies of people sink or float? There is a scientific answer to this question.
The buoyancy of a corpse depends on many factors. Photo source: iflscience.com
Do human corpses sink?
We have already told you that even a person who cannot swim can take measures that will allow him to stay on the surface. And the main “enemy” that leads to death, even when a person is given help, is panic. The thing is that a person literally consists of water – our eyes, skin, muscles and even bones contain water. Therefore, we have about the same density as water, so we have a fairly high buoyancy. For example, when our lungs are filled with air, it is not difficult for us to stay on the surface of the water.
People who can swim may even have difficulty diving to the bottom, but if you exhale air from your lungs, you will begin to sink under water. In fact, when people drown, they actively exhale air due to panic, choke on water, and this does not allow them to stay on the surface. It follows that a dead body, if it loses its buoyancy properties, will begin to sink under water.
A drowning person's lungs are empty of air. Photo source: chips-journal.ru
However, people do not always have air in their lungs at the moment of death. Much depends on how exactly the person died. If he drowned himself, then with a high degree of probability his body will sink to the bottom, since there will be no air in the lungs. If the person died himself, and then his body fell into the water, then in this case there will be air in his lungs, which means that it will not sink under water, or, at least, will sink slowly.
In addition, much depends on the density of water. In a 1977 study, scientists found that 69% of men with average lung capacity float on the surface of salt water. In fresh water, only 7% of bodies do not sink. Therefore, in the movie “Titanic” we were, so to speak, deceived – Leonardo DiCaprio's character could not sink so quickly, given that his lungs were filled with water, and the water itself was oceanic and had a high density.
How quickly does a human corpse sink under water
One study showed that drowning people whose lungs are filled with water dive into fresh water for an average of less than 7 seconds. The maximum dive time was about 10 seconds. What is the reason for this difference? It should be taken into account that the dive time is affected by the current and body type. As we have already said, it is easier for an overweight person to stay on the surface due to the higher fat content in the body. As is known, fat is lighter than water.
Buoyancy depends on the density of the water, the characteristics of the body and other factors. Photo source: www.sport-express.ru
Understanding how quickly the human body sinks is important in search operations. This knowledge can significantly affect the approach needed when searching for a drowned person.
What happens to the body in water after death
As mentioned above, dead bodies often float and are washed up on the shore. But why do bodies sometimes become buoyant after death? The reason lies in the processes that occur with the corpse. As a result of rotting and decomposition, gases are formed.
When a person is alive, in fact, the biological balance in the body is disturbed, which is related to our immune system. It does not allow bacteria to multiply and spread throughout the body. But when a person dies, the immune system stops working, and everything returns to balance. Bacteria that are in our intestines outnumber our cells by 20 times. After a person dies, they are not limited by immunity and begin to consume everything.
After a person dies, intestinal bacteria spread throughout the body and cause the process of decay. Photo source: doctor.ru
Bacteria enter the bloodstream through the mucous membrane of the gastrointestinal tract and then spread throughout the body. As a result of the vital activity of bacteria, substances in the cells are metabolized. And this begins with sugars that are on the surface. Then they move on to more complex carbohydrates and fats. As a result, the body decomposes, during which a number of by-products arise, among which are many volatile organic compounds.
Some of the gases leave the body, and we feel them as the “smell of a corpse”. But many gases remain inside the body. Therefore, corpses “swell” some time after death. They fill with “air”, which increases buoyancy, and accordingly, the corpse floats to the surface. The time required for the body to float may vary, but on average it happens within a few days, unless, of course, the corpse is tied to anything.
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But the rate of decomposition of the body can be influenced by various factors, from currents to the salinity of the water and its composition. The main factor is temperature. In water, decomposition occurs more slowly than in air. In salt water, the process slows down even more. But decomposition processes can generally stop in cold water. For this reason, bodies in cold water may never float to the surface.