[asqa]

why dead body is floating in water? any answer

[Dude]

Interesting question.  I don't know the answer, but my guess would be that the rate of decomposition of the internal organs is greater than the rate of decomposition of the skin.  The outgasing resulting from bacterial degradation would cause an increase in the volume of the body along with a relatively constant mass resulting in an overall density less than water.  There are probably a lot of other factors involved (water swelling, what is the overall density of the human body before death, etc).  If you are referring to a specific dead body, I have an alibi.  

[Donaldson Tan]

Interesting question ... If you are referring to a specific dead body, I have an alibi.  

Heheh.. Whose your alibi?

As long the skin hasn't punctured, the body should be able to contain gaseous decomposition product. These products contribute to lowering the density of the body, thus the body floats. (perhaps)

[macdonda]

This quote is from the following website: http://www.aaronelkins.com/forensictidbits.htm

Question:  Do dead bodies float?

Answer:  A newly dead human being, or any other animal, will sink when placed in water.  After the gases of decomposition build up in the chest and abdomen, however, the body will inflate, rise like a hydrogen-filled balloon, and pop to the surface, sometimes dragging with it surprisingly heavy weights that a murderer might have thought sufficient to keep it down.   With the passage of time and further decomposition, however, the body cavities eventually rupture, the gas escapes, and the corpse goes down again, this time for good.

There is one notable exception:  sometimes, due to air caught in the clothing, a body will stay on the surface for several hours before sinking.

[lemonoman]

For the most part, bodies float anyways...in swimming classes, they always teach the back- and front- floats...you just lie facedown or faceup and naturally float (unless you're REALLY muscular, since muscle is denser than water).  In the beginning of death, the body goes limp (just before rigor mortis   )...and thus should float??  Maybe??

[sdekivit]

the main reason why a dead body will float is mentioned: decomposition of the body cause the body to fill up with gasses.

The body will first sink due to the rigor mortis. Because there's no ATP the myosinheads stay attached to the tropomyosin causing the contraction of the muscles and thus a higher density of the body then water

[Borek]

The body will first sink due to the rigor mortis. Because there's no ATP the myosinheads stay attached to the tropomyosin causing the contraction of the muscles and thus a higher density of the body then water

Do you mean that stiffened muscles have significantly smaller volume?

I doubt rigors mortis has anything to do with the body floating or sinking. When I take full breath I can lay on the water. When I blow the air I can lay on the pool bottom and pretend to be drowned (not for long though ).

Air in the lungs & Archimedes law do the trick. Nothing else matters.

One thing worth mentioning: if the drowned body lies deep enough, it will not surface, as the external pressure will prevent gases buildup.

[tortoise]

The gas of decomposition is O₂ that has penetrated to the body so that it can make the bosy float? Does O₂ oxydize the body?

[savoy7]

I thought I'd put my 2 cents in.  The intestinal tract (GI tract) has its own natural flora (bacteria) living in it - in a sense - outside of the body.  The conditions in the GI tract are anaerobic, so anaerobic respiration occurs.  Some by products of anaerobic respiration are:  methane, CO₂ and hydrogen to name a few of the gases.  Some of these gases are produced when you are alive:  like gas or flatulence.  These gases will cause the gut to expand and buoyancy.

When I try to preserve a specimen for a collection.  I have to open the gut and suck out the liquids.  Then I inject a preservative.  If I don't cut open the gut, the animal explodes (tears) and it is destroyed.

[Karakth]

So theoretically a victim of murder by stabbing, where the puncture wounds have ruptured the body cavities and the gut will not float up to the surface, since the gas escapes through the holes?

Or are ruptures not enough, with actual sterilization being required?

[Borek]

So theoretically a victim of murder by stabbing, where the puncture wounds have ruptured the body cavities and the gut will not float up to the surface, since the gas escapes through the holes?

No. Holes will close due to clotting, regardless of whether you are still alive or already dead (of course to the limit - but as long as we talking about deep punctures they will be effectively closed as the process of clotting will continue even after you will be pronounced death by the medical standards - ie no heartbeat/breathing/electrical activity of brain).

[gregpawin]

Just recently, during the coverage of the hurricane Katrina blitz, Slate covered a question asking whether or not bodies always like to float face down.  It kind of covers this question also:

http://www.slate.com/id/2126310/