Navy Seal soldiers may not wear underwear because of the circumstances that they are put in during their tours of service. In the long stretches spent in humid and wet environments, soldiers choose to forgo underwear because of the possibility of fungal infection.
Navy Seals are often away for long stretches of time without the ability to wash their underwear. Underwear can take up precious space in rucksacks. Another reason soldiers are likely to forgo underwear is because of a very serious condition known as crotch rot. This condition can affect soldiers in hot and humid locations, and has the potential to put them out of action. Underwear also causes chaffing during longer physical activities.