Why do bodies placed in water initially sink but float eventually

A. A living person has almost the same density as water. If the person is alive and breathing, they will float, but if they drown they exhale and sink as water takes the place of air in the lungs.

After death the body decomposes. Bacteria feed on the decaying flesh, excreting gases, which inflate some body parts, mainly the face and abdomen. Once enough gas has built up inside the body it becomes buoyant and surfaces.

If the water is cold enough, decomposition may not occur and so the body remains submerged.

To read more about the effect of temperature on decomposition, click here.

Q. How long does it take for a body to float back to the surface

A. This depends on a number of factors including the depth and temperature of the water, the amount of sunlight the body receives, and whether some object traps it underwater.

Q. If a body is weighed down will it still float eventually

A. Normally yes. Even if a body is trapped under water by its legs by a submerged object the gases will keep forming until it is buoyant enough to detach itself from the trapped leg and rise up.

Q. Do bodies always rise spine upper most

A. Sometimes women and overweight people can rise facing upwards because of the large build up of gases in breasts and large abdomens.

Q. How quickly does a body decompose in water compared to above water

A. It roughly takes twice as much time for a body to decompose in water than in air.

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by Lisa Cardy