Hydrostatic weighing in a swimming pool with the FLOATAWEIGH. 
Hydrostatic weighing system with an EXERTECH stainless steel tank.
Hydrostatic weighing (underwater weighing) provides a beautiful, low tech way to answer an important question: How lean are you (really)? Weighing yourself on a bathroom scale does not answer that question very well. The bathroom scale won’t tell you how much of your body weight is muscle and how much is fat, but hydrostatic weighing will. That’s because fat weighs less than water while muscle and bone weigh more than water – fat floats but lean tissue sinks. So by simply floating in a pool of water while being weighed, you can monitor your lean body mass and percent of body fat. If you are losing fat or gaining muscle, your underwater weight will increase. It’s that simple.
Click the link to see a video of the procedure: https://www.youtube.com/watch?v=yk-WLB4Jyq4
The FLOATAWEIGH is an ingenious new way to find out how much people weigh in the water. It is a weighing system on floats that can be used in any swimming pool. A weighing platform is suspended underwater from electronic force transducers (load cells). The weighing system is powered by rechargeable batteries and the weight is transmitted to your computer by radio waves. With either the FLOATAWEIGH or a traditional immersion tank, percent of body fat and lean body mass are calculated using the same great EXERTECH software that is used by research universities.