why wrecked dead bodies floats only on third day of death?

Answer 1

Often, clothes, shoes, stuff in pockets add weight which cause the bodies to sink initially. (That's why people drown when they go in the water fully clothed, with shoes on -- and why they have to start peeling off shoes and clothes fast to stay afloat.)

After a while, decomposition sets in, and gases build up inside the body, causing the bloated body to float to the surface.

If you want more explicit details, here's this:
http://kirklea.blogspot.com/2005/09/why-bodies-in-water-float.html

Answer 2

Actually it depends on the temperature of the water. Clothing and jewelery and such are minor factors. Usually the person inhales or swallows water prior to death and this decreases his buoyancy. The temperature of the water will determine the rate of putrification, with subsequent gas release into organs such as the intestines. Most corpse look bloated, as they are indeed fill with various gases. The different gases are strong enough that dogs can be trained to discover bodies under water. Total decomposition under water is unlikely as the bacterial and gas evolution causes buoyancy...unless the corpse is weighted or trapped under water. Strangely both sea decomposition and fresh water decomposition of a corpse are almost the same and the bodies float up in about 72 hours or longer in cooler waters, but obviously warmer waters hasten the multiplication of the bacteria and decomposition and in tropical areas, bodies often float within 24 hours.

Answer 3

The body absorbs water in this period of three days and the density becomes almost equal to water. However the decays within body may generate some gases and make it float.

Answer 4

That is usually the time decomposition starts and nitrogen starts filling the body and since air is lighter than water, it floats but because the bady is heavy, it does not float in the air.

Answer 5

I think it's because of all the gases that build up inside your body. I'm not too sure, but it's like when you see something dead on the side of the road and they bloat up, well it's like us.

Answer 6

The buildup of gas from decomposition bloats them.