The added resistance is a resistance component that is not yet satisfactorily predicted, although its accurate estimation is crucial-both from an environmental and economic point of view-from the design stage of a ship until its operation. One of the possible sources of overprediction is the occurrence of bow wave breaking. The first aim of this paper is to study the effect of bow wave breaking on added resistance by combining visual observations with resistance tests. On the other hand, as the bow region of a ship appears to be the most dominant contributor to added resistance, this paper introduces a dynamic waterline detection method involving stereo vision. This experimental method is applied to reach the second aim of this paper, which is to stress the importance of the relative wave elevation in the bow region of the ship. By placing stereo rigs inside the hull of a semi-transparent ship, the waterline at each momnent in time can be tracked using an edge detection algorithm. By performing resistance tests on the Delft Systematic Deadrise Series ship model no. 523, the added resistance is observed to be proportional to the relative wave height squared. The data of the experiment and the information necessary to reproduce the experiment are shared through https://doi.org/10.4121/19525852.