Ducks can float for long periods of time; their bodies are well adapted to being able to do it effortlessly. Their feathers repel water, preventing them from getting soaked so they can maintain buoyancy. They also have air sacks within their bodies that reduce their overall density. They also have an innate ability to swim and use their webbed feet to propel themselves and can swim efficiently across the water at about 2-3 miles per hour.
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From @mmckinneyphoto13