Let’s start with displacement/length. Displacement is a measure of how much water a particular hull form displaces, and length is, well, length. In general terms, the lower the D/L ratio is, the less water is being displaced for a given length, which would indicate better performance. Performance, though, often reflects speed, but not necessarily comfort, underway. Long-distance cruisers might get there fast on a boat with a very low D/L figure, but they might not get much sleep along the way because of the boat’s lively movement in a seaway.