Shadow zones in Underwater Wireless Sensor Networks (UWSNs) dramatically impact communication system performance. In this paper an adaptive topology reorganization scheme has been proposed that is able to maintain connectivity in multi-hop three-dimensional UWSNs affected by shadow zones. The optimal placement for the sensor nodes to minimize the transmission loss and to maintain the network connectivity has been found using our proposed mathematical model. The theoretical analysis and the numerical evaluations reveal that our proposed scheme reduces the transmission loss under all propagation phenomena for all water depths in UWSNs and improves communication quality.