When a human dies, several biological processes kick in that can affect whether the body floats or sinks in water. Initially, after death, the body may sink due to its density. However, as decomposition begins, gases start to form within the body, mainly due to the breakdown of tissues by bacteria. This process of decomposition usually occurs about 3 to 5 days after death, depending on environmental conditions.
These gases accumulate in the body’s cavities, such as the abdomen, and make the body less dense than water. Once the gas buildup increases sufficiently, the body will rise to the surface and float. This is especially true in warmer waters where decomposition happens more rapidly. Furthermore, factors like the individual’s body composition prior to death, clothing, and water conditions (such as salinity and temperature) can also play a role in whether the body floats or sinks.
In summary, a human dead body can float due to the gases produced during decomposition, which lower its density compared to the surrounding water, thus causing it to rise rather than drown.