## 1 Introduction
### Motivation and Contribution  
A developing network technology made up of sensor Rx nodes is mostly used for detection systems, submerged advanced warning, and aquatic environment element surveillance [28; 33]. The connection quality of all these nodes are impacted by extra components including the Doppler frequency shift and ambient noise disturbance because of the submerged channels complexity [41]. The rate of communicating data packet transmission, the stability of transmitting data, network throughput, and energy usage of UWSNs are all directly impacted by these interferences. Consequently, it is a very difficult challenge to figure out how to send the collected information efficiently and quickly to the destination node. Data packet transmission from the Tx anchor node to the sensor Rx node in the network is guaranteed by MAC and routing protocols. The submerged habitat is complicated and unstable, and underwater sensor Rx nodes have relatively limited processing, memory, and communication resources. Due to the unique properties of UWSNs, including high power consumption, high transmission delay, and dynamic structure [42], the MAC and routing techniques offered for terrestrial wireless sensor networks cannot be simply adapted to underwater networks. Compared to UWSNs, the MAC and routing protocol of UWSNs is more complex and constrained. As a result, the submerged routing and MAC protocols should be able to provide very credible and efficient communication connections for the system in challenging underwater conditions. Scalable submerged routing and MAC protocols are required to support dynamic network updates and network stability during a wide range of circumstances. The route for transmitting data from submerged Tx anchor nodes to surface sensor Rx nodes is often chosen using routing and MAC protocols. Many publications about underwater MAC and routing protocols have been published recently as a result of an increase in the number of scholars who are interested in the study of underwater networks. The protocols for underwater routing and MAC were summarized in other papers. The majority of them, have worked on the secure data communication with having constant data rates in changing environment. However, in this study we focused on the efficient energy methodologies so to increase the life span of our opted co-operative networks. Abbreviations table, shows the abbreviations of our article.  
The following are the major contributions of this work.  
Based on energy efficiency, we assessed several MAC and routing protocols in this study for which the process of sending and received data packets from source to destination is shown in Figure 3 for the better understanding of the readers.  
Figure 4 displays the RTS/CTS outcome for the carrier sense multiple access (CSMA) MAC protocol from the source to the destination communication in UWSNs with the Buffering_Slotted_ALOHA protocol network topology shown and elaborated through Figure 5.  
On the basis of routing techniques, we proposed a new classification of current E2 RPs that is specially tailored for UWSNs.  
We explore the key ideas, guiding principles, benefits, and drawbacks of different proposed works, and offer a comparative analysis of routing algorithms with also providing a reliable cooperative routing strategies for UWSNs in terms of energy efficiency.  
Figure 3: Procedure of sending and receiving data packets [43].  
The remaining portions of this paper are listed below. In Section 1 provides a description of the introduction. Section 2 provides characteristics of UWSNs transmission. In Section 3 we discuss about the different challenges, while designing any MAC protocols in UWSNs. In Section 4 we categorized different MAC protocols in terms of their energy efficiency in UWSNs. In Section 5 we compared different routing protocols in terms of energy efficiency in UWSNs. The current problems and research difficulties pertinent to constructing an E2 RPs for UWSNs are discussed in Section 6. Section 7 wraps up our research.