March
As cruising speed at a designated one vessel under machine , the traveling speed at which the ship can be driven most economically, ie with a given amount of fuel is the furthest.
At ever higher speeds, the water and air resistance increase disproportionately, at lower and lower speeds, however, the efficiency losses due to the (largely constant) internal requirements of the machinery. The cruising speed is the speed with the best ratio of fuel used and distance traveled.
The cruise is different for each ship because of its dependence on the shape and size of the ship and the type of propulsion . The draft, which is dependent on the current load , also plays a role, as does the respective wind and current conditions - if a ship hardly makes speed over the ground during "normal" cruising with strong countercurrent and strong headwind, the speed has to be increased, otherwise it will too high a percentage of the fuel consumed is only needed to overcome the current.