Iteration 1: Quick and Dirty -- Humpback's are good at going long ways efficiently during their migrations. Maybe use that as a starting point. Downloaded some 3d models of whales, concept to do an area rule and make hull shape similar. Looked for research papers on hydrodynamics of cetaceans.
An indicator of streamlining is fineness ratio (max dia/length) 4.5 gives least drag and surface area for maximum volume, although only 10% drag increase in FR of 3 to 7.
Dolphin body form similar to 2d airfoil NACA 66-018. Killer whale NACA 66-026. Both laminar flow airfoils