“Float First:” Trapped Air Between Clothing Layers Significantly Improves Buoyancy on Water After Immersion

Abstract

Approximately 450,000 people drown annually worldwide. The capacity of immersed adults and children to float in clothing is less well understood, but it is possible that air trapped between clothing layers increases buoyancy. These studies aimed to quantify buoyancy and the practical implications thereof. Study 1 (n = 24) quantified this buoyancy and the consequence of any buoyancy by measurement of airway freeboard (mouth to water level distance). Study 2 examined the capability of children (n = 29) to float with freeboard used as the outcome measure and is expressed as a percentage of occasions that freeboard was achieved. Buoyancy (measured in newtons; N) was provided for winter clothing as 105(± 12)N, for autumn/spring clothing as 87(± 13)N, and for summer clothing as 68(± 11)N. In all cases, buoyancy was greater than for the control condition of 61(± 11)N. Aver-age freeboard was 63(± 2) % for winter clothing, 62(± 2) % for autumn/spring clothing, 66(± 2)% for summer clothing, and 15(± 1)% for the control condition. Children were more buoyant, 95(± 17)% freeboard, irrespective of gender, than adults. " Float first " is advocated as a primary survival mechanism. An average of 445 people per annum drown in the UK (Royal Society for the Prevention of Accidents, 2002, 2005). The majority of these drowning incidents occurred in inland rivers and streams or in the relatively calm waters of lakes and reservoirs. Many of the victims were young, who had accidentally fallen into the water, were fully or partially clothed, and drowned within a short distance of the safe refuge of land. Indeed, data from the International Lifesaving Federation (Interna-tional Lifesaving Federation, 2010) suggest that approximately 40% of drownings occur within 2 m of safety and a quarter occur in water less than 1 m deep. These data suggest that swimming performance in the early minutes of immersion is impaired. This, in part, is due to the low average annual water temperature in and around the U.K where temperatures reach a nadir of ∼6 °C in spring and a peak of 16 °C in autumn throughout the yearly cycle (Lowestoft et al., 2007-2008). Even