Effects of immersion in water
These, reviewed in standard texts, are obviously influenced by duration and water temperature, but other factors, such as whether the water is still or flowing, fresh or salt, clean or polluted, are also relevant.
Immersion modifies most changes after death. Bodycooling will relate directly to the water temperature. In the United Kingdom cooling in water is roughly twice that in air, and is accelerated in flowing rivers and streams. Onset and duration of rigor mortis are also affected by water temperature: in cold water onset is delayed and duration prolonged. Drowning is a well recognised context in which cadaveric spasm (instantaneous rigor) maybe encountered ("the drowning man clutching at straws"). As most submerged bodies float prone, with arms and legs hanging downwards, hypostasis (lividity )is usually maximal on face, neck, upper anterior chest, forearms, hands, lower legs and feet. In Caucasians it may be appreciably pink, perhaps because immersion facilitates oxygenation through the wet skin after death, or perhaps merely the result of cold. With fast flowing water, the constant movement may impair ,if not inhibit completely, development of hypostasis.
Decomposition (putrefaction) is also influenced by water temperature. In the United Kingdom time intervals associated with the various standard changes are about twice as long as those in air, but may be prolonged further in flowing water and reduced in heavy pollution.In tropical waters decomposition may be established by 24 hours, where as none may be apparent after several weeks in water constantly below 40°F(5°C). With advancing decomposition, gas formation increases buoyancy until ultimately (in the United Kingdom after about three to 14 days, depending on the season), and providing it is free to do so ,the body will float, often, because of intestinal putrefactive gases, belly upwards. Interestingly, once a submerged body is exposed to air after recovery, decomposition often proceeds very rapidly, and this may well continue despite apparently adequate refrigeration. With prolonged immersion, adipocere will form.