This paper presents a clustering protocol combined with a mobile sink (MS) solution for efficient data gathering in wireless sensor networks (WSNs). The main insight for the cluster creation method is drawn from image processing field and namely from the watershed transformation which is widely used for image segmentation. The proposed algorithm creates multi-hop clusters whose clusterheads (CHs) as well as all cluster members near the CHs have high energy reserves. As these are exactly the nodes most burdened with relaying of data from other cluster members, the higher levels of available energy at these nodes prolong the network lifetime eventually. After cluster creation, a MS periodically visits each CH and collects the data from cluster members already gathered at the CH. Simulation results show the higher performance of the proposed scheme in comparison to other competent approaches from the literature.