I've been looking into electric boats and I've learned a lot about hull shape and speed/drag. Boats like canoes and sailboats are "displacement" hulls - they literally push the water around the hull to move the boat forward. A smooth transition at the rear becomes more important for drag reduction. Most recreational power boats are "planing" hulls with the boat riding on top of the water. The less hull in the water the less the drag.
Cars are definitely displacement hulls.
