An apparatus or integrated hull design to stabilize boats with V-shaped hulls. This invention includes a cavity affixed to the inside of the hull confirming to the shape of the inside of the hull. The hull has a step toward the rear of the hull to transition from the V-shape to an essentially flat shape. An opening is provided through the hull and cavity in the step. The cavity extends above water level and is provided with a cover and a vent. The design allows water to enter the cavity enhancing stability when idle or at slow speed and to exit the cavity when at higher speed.