Answer: gallium indium phosphide (GaInP) solar cells
According to the U.S. Navy, high-quality GaInP cells are well suited for underwater operation because they have high quantum efficiency in wavelengths between 400 and 700 nanometers (visible light) and intrinsically low dark current, which is critical for high efficiency in lowlight conditions. Preliminary results at a depth of nearly 30 feet reveal output of 7 watts per square meter of solar cells.
