Abstract: There is provided a boat hull 10 having a keel portion 11, a transom 12 and a deadrise portion 13. The deadrise portion 13 of the hull 10 has a recess 15 in the region of the transom 12 having a substantially planar upper surface 17 and bounded by side walls 20 and leading edges 21. The length of the recess is selected to be about 20% of the overall length of the boat hull 10. The depth of the recess 15 is selected to be about 10% of the length, and is configured such that the upper surface 17 is disposed at an angle substantially parallel to the water trailing from the leading edges 21 when the boat is on the plane. A step 22 is provided such that the upper surface 17 may break contact with the water as the hull accelerates, and the angle .beta. of the leading edges 21 is selected such that the leading edges 21 are substantially parallel to the water surface. A vent 23 is provided connecting the recess 15 to the atmosphere as a vacuum breaker.