1. An underwater sensor for forming an image of the above-the-water environment including items located on or above the water surface, the sensor comprising: an underwater imaging polarimeter that captures an image of the water surface and provides four-component image data equivalent to Stokes vector data and indicative of light passing through the water surface into the water; and a processing unit that receives and processes the four-component image data to generate an image of the environment on or above the water surface.