In other words, excessive multi-hop transmissions can lead to a low data delivery ratio because of network congestion and packet errors. In order to address the problem of the low delivery ratio and to minimize energy consumption of U-sensors, we propose a novel underwater sensor network architecture and routing scheme, namely _AURP_ (AUV-aided underwater routing protocol), that use not only heterogeneous acoustic communication channels but also controlled mobility of multiple autonomous underwater vehicles (AUVs). AURP minimizes the total number of data transmissions by using AUVs as relay nodes, which results in a high packet delivery ratio and low energy consumption. Furthermore, by exploiting controlled mobility of AUVs and the fact that AUVs can move closer to other UASN nodes, a short-range high data rate acoustic channel can be applied [10]. As a result, AURP opens a new possibility for an UASN to provide applications that require mass data transmissions, such as multimedia applications. Figure 1 illustrates the concept of AURP and the network architecture, which consists of U-sensor nodes, gateways (GWs), AUVs, and surface unit/mothership. As shown in Figure 1, in AURP, each U-sensor sends sensed data, using a midrange underwater acoustic channel, to the GWs directly or in a multihop fashion. The GWs forward the aggregated data to an AUV using a short-range high rate acoustic channel when the AUV passes by a short distance from the GWs. When an AUV approaches the underwater sink, it forwards, also using a short-range high rate acoustic channel, collected data to the sink, which will in turn forward the data to the surface unit. AUVs have another acoustic interface for a long distance and low data rate communications to receive control signal and to send urgent data from/to the mothership via a surface unit. The underwater sink and GWs periodically broadcast their interests in receiving data, which are used by U-sensors to choose the next hop node such that the number of hops of transmission is minimized. To verify the performance of AURP, we perform simulations using NS2 and compared AURP with another routing protocol that is based on Directed Diffusion [11]. According to the simulation results, AURP shows a much higher performance in terms of delivery ratio and energy consumption. Other contributions of this work includes that a realistic underwater communication channel model is incorporated with the simulation to obtain more reliable results, as well as various AUVs' movement patterns are considered. It is worth noting that there have been several works that use robotic agents to carry data [12; 13; 14; 15]. However, those works focus on scheduling of mobile elements to prevent buffer overflow rather than considering the overall network architecture and the network performance. Furthermore, our work also consider network energy consumption and the critical issues of underwater communication environment which will significantly affect performance of the real world network operation. The rest of the paper is organized as follows. Section 2 presents problem definitions and model. In Section 3, related work is discussed. Section 4 elaborates our proposed network architecture and routing protocol. In Section 5, the performance of AURP is evaluated by comparing with another routing protocol. Section 6 concludes the paper.