How Much Higher Do Swimmers Ride In The Ocean?

How Much Higher Do Swimmers Ride In The Ocean?

The average difference in buoyancy of the same object in salt water versus fresh water is 2.5%. While differences in buoyancy of certain objects in saltier marine waters can be precisely measured, 2.5% is the generally accepted average difference.

If the average center body depth of a streamlined swimmer doing freestyle in calm seas is 30mm below the surface in fresh water, it seems plausible that the salt water center body depth would be 2.5% higher or 0.75mm higher (0.29 inches).

Over the course of 1 km, if a swimmer is riding 0.75mm higher in the water, with all things being equal between a fresh water and salt water swim (i.e., no currents, calm conditions, straight-line course, same energy output), we wonder how much faster would the swimmer be in terms of time in salt water vs. fresh water. Is there a reader in the open water swimming community who can provide an answer and explanation in scientific and layman’s terms?

Is there a reader in the triathlon community who can provide a similar answer and explanation comparing the relative speed of the same athlete over a 1 km course in fresh water vs. salt water who is swimming with a 2.5mm full body wetsuit?

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