How to improvise temporary buoys from clothing is on physical training curriculum. Shirts may be inflated but trousers
(as in photograph) of duck or khaki make better buoys than shirts. After single knot is tied in each leg and lower two or
three buttons of fly are secured, trousers are flipped through air to trap air pockets in each leg. Mattress covers, sea bags,
laundry bags, pillow cases, and sugar or flour sacks may also be inflated by capping openings on surface. Navy swimmers
also learn how to fight seaweed and cramps, how to board a raft, and how to undress in deep water.

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