Kirsty SELWAY (Univ. Glasgow) Studying the polarized light from extra solar planets could be a powerful diagnostic of atmospheric "biomarkers" - providing clues to the possibility of extraterrestrial life. Moreover, gravitational microlensing provides a unique opportunity to study the amplified light from considerably more distant planets in our search for indications of life. Recently, several authors have begun modeling the microlensing signatures of extra solar planets orbiting the lensed star. Calculations indicate that telescopes with very large apertures (>30m) may be capable of detecting structure on the planetary surface and perhaps even rings or satellites, during a high amplification caustic crossing event. The effect of planetary phase and orientation on the microlensing light curve yields the idea that current 10m telescopes should be capable of detecting planets at moderate phases,whereas larger telescopes would be required for extreme crescent phases. These recent works provide some insight into present and future detectability, but do not consider polarization - modeling the planets as Lambert spheres. We investigate the microlensing signature of an oceanic planet observed during a caustic crossing microlensing event. We model the planet with a wavy ocean surface, applying the statistical treatment of Vokrouhlicky and Farinella (1995) to map the "starglint" - specularly reflected light - from elements of the ocean surface. The polarization signal, characterized by its Stokes' parameters, is differentially amplified as the caustic sweeps across the planetary disc. We investigate how the degree of polarization depends on the physical characteristics of the planetary ocean, planetary phase and orientation with respect to the caustic, and the parameters of the source star and lens. Finally we discuss prospects for detecting polarization signals with current and future telescopes.