In antiquity the coastline south of the city of Crotone seems to have been very different from the way it appears in the modern period. Pliny the Elder describes (NH) an archipelago of five islands that have now disappeared; two of these were still clearly visible in Ottoman pilot books of the 16th century. In the 18th century, paintings of the port and the coast south of Crotone still showed spits of land stretching into the sea that today have been almost totally eroded away. With the aim of checking the historic and iconographic information through field research, in the summer of 2009 the Superintendency began the first campaign of underwater archaeological survey along the 8 km of coast between the Porto Vecchio of Crotone and the locality of La Tonnara. For a period of three months a group of underwater archaeologists systematically surveyed the seabed of the entire area starting from the water’s edge down to a maximum depth of 10 m. All the material of archaeological interest found was then catalogued, geo-referenced and inserted into a GIS system. The same attention was also given to the morphology of the seabed with the aim of gathering information on the geomorphology. Thus, numerous ancient ceramic remains (tiles, bricks, amphorae) were recorded on the external reef of the Porto Vecchio of Crotone, which demonstrate the use of the port basin in the Roman period. Similar remains were also found in the area to the north and south of the city cemetery and in the sea in front of the localities of S. Leonardo and Costa Tiziana. The most interesting survey results were produced near the Irto promontory, today almost completely eroded away by the incessant action of the sea. Here, between the water’s edge and a depth of 6 m, 18 limestone blocks and column drums, two working areas cut into the bed-rock and a number of post holes came to light, clear evidence of an ancient submerged quarry,. The geo-positioning of the materials made it possible to identify their alignment in an east-west direction, and to measure the maximum distance from the present coastline of circa 70 m. The dimensions of the blocks and a comparison with similar material from the excavations on land, dated the quarry between the archaic and Hellenistic period. The presence of ancient promontories, now submerged, is also supported by the direct analysis of the sandbanks in the area which, although did not produce an abundance of archaeological material, showed that certain stretches were so high (just 1.50 m in depth at 300 m from the coastline) that they suggest they were fully emerged in the ancient period, calculating an average rise of the sea level of circa 5-6 m for the entire area. By the end of the campaign it was increasingly clear that Crotone, which has always benefited from the only natural harbour on the route between Taranto and Reggio Calabria, was able to offer ancient shipping numerous moorings protected from the wind that no longer exist, reinforcing its role as a crossroads for maritime commerce.