eli5: Why do drowned bodies sink and then float?
In: Biology
First let’s talk different components of our bodies and their density relative to water.
Simplifying alot but
We have lots of water – obviosuly same density as water.
Proteins/muscle: slightly more dense than water so will sink.
Fat: less dense than water so floats.
Bone – much more dense than water and also sinks.
Finally we have some amount of air within lungs – much less dense than water .
An average weight person is typically on average (average density of the entire body) slightly less dense than water and so they float*. When a person drowns the air within the lungs is replaced with water which changes the overall density to be greater than water and so they sink. Over time decomposition of the body leads to gas accumulation within the body which changes the overall density back to being less than water and so they so float back to the top.
*Used to be a lifeguard and part of the certification was to tread water and support one of the other people in the class for like a minute. At the time I was like 130 lbs and average build – so slightly less dense than water and floated. One of my classmates was probably 200-240 lbs of pure muscle and sank like a rock and another was probably 300 lbs of mostly fat and floated easily. Doing the cerification with the super buff dude was 1000x harder the fatter guy.
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