The environmental conditions are predominantly caused by a specific system of exchange of waters with the Ionian Sea, the thresholds of Otranto and Palagruza separating the Adriatic Sea from the Ionian Sea and deeper South Adriatic from the shallower North Adriatic. Hence, there are three principal water masses in the Adriatic Sea: the Adriatic Surface Water, the Levantine Intermediate Water and the Adriatic Deep Water -every sub-basin has its own characteristic deep water. The small coastal area of Bosnia and Herzegovina is particularly vulnerable because of a very w'eak renewal of waters within Neum Bay (no river run-off, small tides, North-South-dominant winds and freshwater surges).