Terkos Lake Formed by the invasion of sea water, the ancient average area calculated as geomorphological is 25 km2. Although the area covered by the lake changes in certain ratios, it has been subject to dramatic changes over time depending on the region. It can be defined as being the most important water basin of Istanbul, and it is an area where scientific work has not been carried out despite all its natural and special beauties. Whereas, being one of the basins of Istanbul, it has been observed that the works carried out at the technical level were carried out by DSİ and İSKİ. The surface area of the lake is 41 km2 and a total drainage area of 775 km2, is approximately 12 km in length and 5 km in width. It is obvious that the morphological features of the lake area, which is located at the border of the most complex and impressive morphological structures. For this purpose, morphometric studies are carried out on the streams feeding the lake and the findings of some shells in the lake and Black Sea are shared in this study.