The preliminary reconstruction of the Koločep canal basin area is based on geomorphological analysis and interpreted acoustic profiles, as well as on global curves of sea level elevation. Inside the basin, there are 9 acoustic units which have been interpreted as changes between marine and lake conditions of sedimentation. During the last glacial period, an intensive erosion of old sediments emerged in the central part of the basin and after that sediments were transported by watercourses which had their own costal wells and „vruljas“ (watersprings bellow sea) at the locations that are equal to their recent locations. They formed the Mljet river that is today submerged. During the LGM, the waterway of the Mljet river in Veliki Vratnik canal (-50 m deep at this location) got covered with the eolic sand during the arid LGM, resulting in the emergence of a new lake in the depression created by the erosion of old sediments. Series of faults inside the basin were identified by observation of acoustic profiles of sediments that imply their inactivity after the sedimentation of the youngest acoustic units (after the LGM). The eastern part of the basin is still in the process of elevation along the fault which was active during older Pleistocene and Holocene, which resulted in the elevation of the seabed along the fault plane. The vicinity of the Stone earthquake's epicenter points to a possible connection with the events in the previously mentioned fault area.