In this note we unify two physical situations treatable with hydrostatics: an object floating on a denser fluid and an open U-shaped tube with two immiscible fluids. We begin by reviewing the problem of a partially floating uniform, rectangular prism of horizontal area "A" immersed in a denser fluid, with respective densities ?[subscript 1] < ?[subscript h] for the prism and fluid (the subscripts stand for light and heavy): see Fig. 1. We define three horizontal levels within the solid, y[subscript 0], y[subscript 1], and y[subscript 2], corresponding to the bottom, flotation line, and top of the prism. The buoyant force is ?[subscript h] (y[subscript 1] - y[subscript 0])gA upwards, and the weight of the prism is ?[subscript 1] (y[subscript 2] - y[subscript 0])gA downwards. By Newton's second law, these two forces balance at equilibrium. After dividing by the common horizontal area, one obtains: y[subscript 1] - y[subscript 0] divided by y[subscript 2] - y[subscript 0] = ?[subscript 1] divided by p[subscript h].