Physiological Basis of Floating in Water

Specifications are derived for the volume of air necessary to float men with their heads out of water to the level of the first thoracic vertebrum. The derivation is based on (a) proportions of body fat, (b) its density and (c) that of the lean body mass together with (d) residual lung volumes. In order to float all body types of men, including large lean men, 11.6 liters of submerged air are believed necessary. It is shown that loading with wet clothing and typical weapons can increase this requirement to upwards of 23 liters of air.