eli5: Why do drowned bodies sink and then float?

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eli5: Why do drowned bodies sink and then float?

In: Biology

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Not everyone’s the same, but most people are just about buoyant when they’re breathing, so when they stop, all those sinuses and air sacs fill with water. Now that they’re a little denser than their surroundings, the lighter (per unit volume) water pushes them down. But, the water wasn’t counting on all the bacteria that was eating that body and can now go ham since the defenses have turned off with the death of the brain. Those bacteria eventually convert enough of their food into gases as they digest and those gases combine into pockets that are less dense than the surrounding water, so the body gets pushed back up.

As someone who has recovered bodies from waterways… The bodies are almost neutral bouyancy at time of death, but then take water in and loose air from those balloons we call lungs after death causing the remains to sink.

Go float in a pool, and exhale. See how fast you sink without that air in your lungs.

The resurfacing occurs due to mostly natural bacterial flora inside your body beginning the decomposition process. This produces gasses inside the carcass, causing swelling and bloating. This eventually acts just like the air in your lungs and the body resurfaces. Actually much more boyant.

They sink because the air in their lungs gets expelled and they become heavier than water.
They then start to decompose and when there is enough of a gas buildup, they float