The invention relates to a low-resistance hull under a designed waterline, belongs to the field of hull shape design, and mainly relates to the design of hulls under the designed waterline. A propeller is arranged on a ship bow, a shell bossing is designed to be in a spindly shape similar to a cone, the two sides of a transition position between the shell bossing and the hull above the shell bossing are respectively provided with an arc flow guide water groove, the bow waterline above the shell bossing is designed to be in a V shape with the big end up, and the V-shaped bow waterline has a flow guide effect. An area which has a small included angle between the surface normal of the bow and the navigation direction is designed to be close to one fourth to three fourths of ship width, two inclined flow guide water grooves are formed in the two sides of a main engine space located on the lower portion of the ship bow, a symmetric ship bow or an asymmetric ship bow is used, and the stern of the hull is designed to be a streamline reducing body. The bow and the stern are respectively provided with a flow channel which penetrates through the larboard and the starboard, and a spraying propelling unit is arranged in the hull to meet the steering requirement of the hull. Through linear bow and stern design and the propeller arranged on the bow, the head and wake flow fields of the hull are improved, adverse effects of water on ship navigation are weakened, and ship resistance is reduced.