## 2 Literature Review  
This section contains the achievements and drawbacks of various routing algorithms and determines the main theme of all the schemes. The scheme proposed in [14] is another cooperative fashion routing for underwater WSNs. Due to the division of the entire network into four equal regions, the scheme decreases the energy consumption and improves the network reliability. In an individual region, both the relay and destination nodes are preferred over the information of maximum residual energy and minimum depth value. A list having information of all neighbor nodes of source is set, in terms of depth information and residual energy value in descending fashion. The source broadcasts a hello bag to know about neighbors necessary information and later to share such information with them. The destination node receives two copies of information packets, from source and relay, which are further merged by using a combining technique. The scheme decreases the energy exhaustion and ensures the maximum information at the sink node, while it increases the latency the death rate of nodes. The authors present a cooperative algorithm in [15] to minimize the network energy consumption and cope with unwanted channel conditions. It selects the destination and the relay nodes by considering the power level of a signal in response to noise level (SNR) and the physical distance among the neighbour nodes. A node forwards the information over the minimum path loss channel. For best forwarder node, the source node first collects the information of all neighbor nodes in terms of SNR and each node physical distance. The node having maximum SNR value and closed to the sink node is taken as destination. The relay node is also selected through the above criteria as a second node. The proposed scheme reduces the exhaust energy and maximizes the throughput. However, it has computational complexity due to calculation of SNR at every link. A cooperative and reliable routing scheme for underwater WSNs is proposed in [16]. In the scheme, the selection of destination node is based on the minimum residual energy and least depth. The relay node is also chosen by using the depth information and remaining energy value. The source node broadcasts the packet and holds the information of neighbors in a list. The source node then forwards. The algorithm utilizes the flooding phenomena for the communication of information packets, while the network congestion is reduced by using depth threshold. It renders maximum packets to the sink node but exhausts excessive energy. In the routing scheme proposed in [17], the authors utilize the distributed delay sensitivity routing algorithm. The approach has two objectives i.e., to improve the channel adaptability simply by forwarding the string of small packets during broadcasting and reduce the packet error rate by retaining the size of the broadcasted information packets. Channel transmission power, optimal node selection, and maximum information forwarding at the low cost of energy are the aims of the scheme. For delay reactivity, the scheme uses the random mobility of the nodes, which utilizes the node velocity and network density. It reduces the latency and improves the PDR while consumes high energy. In [18], [PERSON] et al. proposed an algorithm for underwater WSNs which reduces the latency of information during broadcasting. According to the scheme, when a node in the network forwards packets, then it waits for a certain time. The packets are transmitted frequently for a calculated interval of time with calculated transmission probability denoted. The best forwarder node receives the packet with a fixed calculated probability in the network. The transmission process is successful if the destination receives the packets. In this approach, due to the lack of channel reservation, the network throughput and delay are influenced by the transmission rate. Moreover, the attributes of the scheme are free from the distance between the nodes which overcomes the void space problem.