Post-mortem decomposition is significantly altered when a body is submerged in water. Unlike a terrestrial environment, water introduces unique physical and chemical dynamics that affect the timeline and appearance of decay. The aquatic medium influences how quickly the body cools and the chemical reactions that transform soft tissue, which helps determine the post-mortem interval.
Initial Physical Changes Upon Submersion
The most immediate and striking change upon submersion is the accelerated cooling of the body, a process called algor mortis. Water is a much more efficient conductor of heat than air, meaning the body loses its core temperature four to five times faster than on land. This rapid heat loss brings the body’s temperature closer to that of the surrounding water, complicating the estimation of time since death.
A submerged body initially sinks because the average human density is slightly greater than water, especially if the lungs are filled with water from drowning. The initial sinking time for a drowning victim is often very fast, sometimes less than ten seconds. Shortly after submersion, the outer layers of the skin begin to absorb water, leading to a condition known as maceration. This creates the appearance of “washerwoman’s skin,” a wrinkling and softening of the palms and soles that becomes apparent within hours, causing the outer layer of skin to eventually peel away.
Environmental Factors Influencing Decomposition Rate
The speed at which a submerged body decomposes is dictated by the external environment, with water temperature being the most important variable. Cold water significantly slows the chemical reactions and bacterial activity responsible for breaking down tissue. For example, a body in very cold, deep water, where temperatures remain near freezing, can be preserved for an extended period.
Water movement, such as strong currents, can affect the rate of decay by accelerating the loss of tissue and bone through abrasion and scavenging. Conversely, in deep, still water, the lack of oxygen and lower temperatures create an environment that slows microbial action. The level of salinity also plays a role, as decomposition tends to be faster in fresh water compared to saltwater environments, where high salinity can inhibit some bacterial and fungal activity.
The Specific Process of Adipocere Formation
One distinct outcome of decomposition in a wet, cool environment is the formation of adipocere, also known as “grave wax.” This chemical transformation replaces typical putrefactive decay and acts as a preserving agent for the body’s contours. The process is chemically known as saponification, the hydrolysis and hydrogenation of body fat.
Saponification involves anaerobic bacteria, such as Clostridium perfringens, breaking down neutral fat triglycerides in adipose tissue. This reaction converts unsaturated fatty acids into insoluble saturated fatty acids, predominantly myristic, palmitic, and stearic acids. The resulting substance is a grayish-white or tan, crumbly, waxy material, ranging from paste-like in its early stages to brittle and hard over time. Adipocere formation requires high moisture and low oxygen, characteristic of submerged bodies.
Understanding Buoyancy and Flotation
A body that initially sinks will resurface due to internal changes driven by bacterial activity. Putrefaction involves the breakdown of tissues, which generates significant amounts of gas. These gases, primarily methane, hydrogen sulfide, and carbon dioxide, accumulate in the body cavities.
The trapped gases cause the body to inflate, which reduces the body’s overall density. Once the body’s density becomes less than that of the surrounding water, it achieves positive buoyancy and floats to the surface. The time it takes for a body to rise, often called the “float time,” is highly variable, but in warm water, it can happen within a couple of days, while colder temperatures can delay the process for several weeks. Eventually, the continuous production of gas can cause the body cavity to rupture, allowing the gases to escape and potentially causing the body to sink again.