I do not study biology at all. Is it known if sharks who evolved over milion of years have more hydrodynamical shape than say e.g. dolphins who evolved for much shorter time. It probably depends on many factors e.g. how fast on average a predator swims, strategy of hunting etc. I think marlin have quite hydrodynamical shape. Generality of this question (which I do not want answer) is how fast evolution produce certain quality. It probably is not a gradual process, I think. To sum it up: my question is about hydrodynamical shape of body of two species (sharks, dolphins). And second part is: if time of evolution of given species plays a role in hydrodynamical shape?