There must be a grain of truth in what is said by Imhoff and Pranger, otherwise the world’s top swimmers would not be wearing the newest range of sharkskin inspired suits, which were worn in more than 90% of the winnning swims at the Beijing Olympics.
However, the sharkskin technology relies on the water flowing the right way over the “denticles” and purely having a rougher hull may not be sufficient to make that much of a difference.