## 1 Introduction  
The Earth's surface is 70% covered by water, where vast amounts of resources lie unexplored. Recent developments in sensor network technologies and emerging underwater sensor networks (UWSNs), have made the development of underwater applications feasible. The importance of underwater applications is attracting the attention of researchers which in turn has led to the rapid growth of research within various areas in Underwater Acoustic Sensor Networks (UASNs) [1]. UASNs comprise sensor nodes capable of sensing, processing and communicating the sensed data to the appropriate destination which are deployed underwater for an effort in backing vast range of applications in collaborative monitoring tasks [2, 3]. Recently, many researchers are focusing on how to develop different underwater applications to support the lives of living organisms underwater and even those that are living on the sea floor by the use of collaborative, cooperative and frequent monitoring of underwater environments [4]. Recently, the frequent occurrence of disasters such as the sinking of USS ship name missing [5; 6], the Kursk submarine disaster in Russia [5; 6], the recent search for survivors of the Argentinian submarine ARA San Juan, and the Deepwater Horizon oil leak in the Gulf of Mexico [6], have encouraged several research teams to carry out various oceanic monitoring applications of UASNs such as oceanic surveillance applications [7], environmental monitoring, chemical exploration, military applications, and safety applications [4]. In UASNs, the exchange of information is the primary goal, and it can be achieved among the nodes within a stipulated network coverage area or outside the network coverage using a gateway device (e.g., sink). Underwater sensors are usually energy constrained since the nodes are battery powered. Therefore, to conserve more energy, transmitting packets in several small hops is helpful. By combining more underwater applications from private companies, government and non-government organizations, a single authority network would not be feasible. Therefore, the network can benefit from multiple authority network, where energy consumption can be reduced by cooperation between different authorities to forward the packets to the surface station. Also, packet delivery reliability can be improved and enhanced by cooperation between authorities. However, a new challenge may arise, where a single selfish authority or node can exploit the cooperation behaviors or in case of a malicious authority the data security can be threatened. In these regards, cooperative communication techniques providing reliability in packet delivery for UASNs remains unexplored [8]. Acoustic waves are capable of being transmitted through the water to distances that are operationally significant. Because of this, sound is the physical phenomenon used for underwater communications. In underwater applications, an acoustic signal is a sound waveform which is usually produced by transducers. Even with noise and uncertainty, an acoustic signal processor is capable of extracting information from the acoustic signal [9]. In UASNs, sensor nodes are wirelessly interconnected with one or more underwater sinks (UW-sinks) via acoustic links. UW-sink can be connected with sensor nodes by two methods, either through direct links (DL) or through multi-hop (MH) paths [10]. These underwater sinks are responsible in relaying the sensed data collected from the sensor nodes situated in a particular location in the ocean to the surface station [11] as depicted in Figure 1[11; 12]. Each UW-sink is mainly equipped with some form of transceiver such as horizontal transceivers, which are used by underwater sinks for communicating the configuration data and commands with sensor nodes (UW-sink to sensor) and also collect the sensed data (sensor to UW-sink). Vertical  
Figure 1: Cluster-based architecture of UASNs. transceivers are used by UW-sinks to relay the collected data to the surface station.