A multiphase-liquid level sensing system for sensing a layer depth and thickness of a liquid of a first phase that floats on a liquid of a different second phase includes an elongated stem that defines an elongated cavity. A float, which exhibits a sensible property, is disposed coaxially around the elongated stem and has negative buoyancy relative to the liquid of the first phase and positive buoyancy relative to the liquid of the second phase. A level sensor senses the sensible property and indicates a second phase liquid distance from the float to the bottom of the stem. An overburden sensor extends downwardly from the stem senses total liquid thickness of the liquid above the overburden sensor. A computational circuit calculates a layer depth and thickness of the liquid of the first phase, based on input from the level sensor and the overburden sensor.