Underwater acoustic sensor networks typically comprised of sensor nodes that are deployed in sufficiently large numbers for data collection, monitoring and surveillance. Multi-hop relay transmission manner is used to deliver acquired data from sensor nodes to the sink node; nevertheless, hot spots around sink node will bring severe problems. In underwater sensor networks model of this paper, nodes are divided into two components: static sensor nodes and mobile UUV (Underwater Unmanned Vehicles), i.e., conventional sink node is replaced by mobile UUV. The mobile UUV in this novel framework takes charge of collecting sensory data from different sensor nodes and delivering all the sensory data to the monitoring center. Comparing with traditional model of underwater sensor networks, it is beneficial to use mobile UUV to ferry sensory information instead of using multi-hop relay transmission method, because the energy of sensor nodes in harsh oceanic environment is very limited. In order to improve energy efficiency, we therefore proposed a novel UUV mobility management scheme for underwater acoustic sensor networks that aims to achieve robustness and energy efficiency under harsh underwater acoustic channel conditions. The proposed mobility management scheme determines UUV movement routing using directional metric functions considering location information and energy level of sensor nodes. Furthermore, a hierarchical model based on cluster structure is induced where sensor nodes are grouped into clusters after they are deployed, therefore, UUV will only collect fused data of cluster heads but not every cluster members, thus to simplify route of UUV. Finally, the simulation results verified the efficacy of the proposed mobility management scheme.