Aquatic & Hydraulic Ingenuity - Floats for Walking on Water

Leonardo thought about how soldiers could cross stretches of shallow water. He suggested that inflated skins (leather bags or wineskins) could be strapped to the soldiers' feet. If they were large enough, they would bear a soldier's weight. Floatable wooden planks might also be used.
Two poles, also with inflated bags at the ends, would help with balance and might also be useful in pushing forward through the water.
Leonardo's idea was impractical for water, but similar principles are used today by cross-country skiers.