Ship hydrodynamics in the nineteenth century was dominated by John Scott Russell’s wave-line theory. Russell, a prominent British shipbuilder and scientist, argued that wavemaking was the primary source of resistance for ships, and that by designing ships according to trigonometric curves and proportions (the wave line) this resistance could effectively be eliminated. From the 1840s to the 1880s, shipbuilders such as John Willis Griffiths, Donald McKay and George Steers designed their clipper ships (like Sea Witch and Flying Cloud) and yachts (America) with wave-line hulls, while authors like Jules Verne referenced Russell’s theory. The wave line slowly faded after William Froude developed his laws of ship resistance. The article examines how Russell’s theory became accepted by technical experts and the wider public to become the most widely known ship hydrodynamic theory of the 1800s—a reminder of how a persuasive idea can take hold of an entire profession, and even the public, for a long time.