An estimated 4.1 million people in the United States participate in recreational sailing. Yet the large library of sailing literature leaves many of them high and dry. On one side are technical guides for America's Cup boat-builders; on the other, simplistic books for weekend sailors with little interest in science. In Float Your Boat! professional and amateur boaters alike will find intelligent and understandable answers to such questions as: What were the key innovations that made sailboats more efficient? How do you increase the speed of a boat? How do sailboats travel into the wind? Why are so many explanations of sailing so wrong? Sailing enthusiast and physicist Mark Denny first traces the evolution of the sailing craft, from prehistoric coracles made of animal skins and antlers to the sailboat's reinvention as a pleasure craft during the Industrial Revolution. He then identifies specific sailing phenomena--how wind drives modern Bermuda sloops, how torque determines stability, why hull speed exists--and provides the key physics principles behind them. Whether you are an inquisitive landlubber who has never set foot in a boat, a casual weekend sailor, or an old salt who lives for the sea, Float Your Boat! is an accessible guide to the physics of sailing.