The Aegean Volcanic Arc currently has active hydrothermal activity in the regions of Euboea Island, Susaki, Methana, Milos, Santorini, Kos Nisiros and Yali. The island of Milos, where the volcanic system has been stable since 205 AD, probably has the greatest area of active submarine hydrothermalism with an estimated 34 km2 of active sea-bed. This venting inputs nutrients (ammonia, phosphate, silicate and iron) and carbon dioxide into an sea. The venting areas may be detected by increased temperatures, water turbidity and bubble plumes. Maps of these areas can be compared with chlorophyll concentrations to ascertain how they affect the biological productivity of the region. Photography of the shallow water areas should also show changes in the sea grass and minero-bacterial mat distribution since ground surveys were last undertaken in 1997. In contrast, a similar area of previously stable venting activity off Panarea, in the Tyrrhenian Sea, had a volcanic eruption, creating a tsunami, in December 2002. A similar aerial survey will provide data on how activity has changed and productivity affected since the eruption. This is an unparalleled opportunity to compare the effects of shallow water venting between "active" and "stable" venting sites in the Mediterranean.