As a forensic expert with extensive experience in the field of body decomposition and its interaction with water, I can provide a detailed explanation of the factors that influence whether a drowned body floats or sinks. Initially, a body that is submerged in water will typically sink due to its density being greater than that of water. The air that is present in the lungs and other air-filled spaces within the body can initially cause the body to float, but as the air is gradually replaced by water, the body becomes denser and sinks. However, the situation can change over time. As the body begins to decompose, particularly after a few days, bacteria within the body start to produce gas, including methane, hydrogen sulfide, and carbon dioxide. These gases can accumulate within the body, increasing its buoyancy and potentially causing it to float to the surface. The production of gas is one of the reasons why drowned bodies are sometimes found floating. It's important to note that the process is not uniform and can be influenced by various factors such as the body's composition, the temperature of the water, and the presence of clothing or other materials that could trap air or affect buoyancy. read more >>

As a general rule, yes. A cadaver in the water starts to sink as soon as the air in its lungs is replaced with water. Once submerged, the body stays underwater until the bacteria in the gut and chest cavity produce enough gas��methane, hydrogen sulfide, and carbon dioxide��to float it to the surface like a balloon.read more >>