Re: Do you drown faster in salt water or fresh water?

Hi Heather:

Well, humans can't breath underwater, so a person immersed in either salt or fresh water will drown in about the same time.

However, people tend to float much better in salty water than in fresh water. Anything floating in water is held up by a force we call buoyancy. Basically, buoyancy is caused by the difference in density between the water and an object floating in it.
Salty water is more dense than fresh water - it has a bunch of salt dissolved in it, so its weight per unit volume is higher. That makes the difference in density between a person and the water they're floating in larger, and makes them more buoyant (they'll float higher in the water). This is somewhat noticeable in the ocean, but is particularly apparent in very salty water, such as is found in The Dead Sea, or the Great Salt Lake in Utah. In both of those lakes the water is so salty that a person will float on the surface very easily (in fact, if one swam below the surface that buoyancy force would cause them to float back to the surface as soon as they stopped swimming).

So, although a person will not drown faster in fresh or salt water, it's much harder for that to happen in salty water.

Hope that helps!
Rob Campbell, MAD Scientist