## 2 Related Work  
Research on underwater sensor networks has picked up the pace in recent years, and many advancements have been made. This motivated many attempts from researchers to present complete surveys on the advancements. This section will attempt to describe previous works and compare them with this paper briefly. * [PERSON] et al. [13] give an overview of the architecture and the requirements of UWSN. They broke down the requirements into five parts: longevity, accessibility, complexity, security and privacy, and environmental sustainability. They also introduced thematic taxonomy for UWSNs such as architectural elements, underwater acoustic communications, routing protocols, security, and application. The distinguishable difference between this paper and our paper is that we discuss the protocols and their propagation path. This will help readers in choosing the correct protocol for their system. * [PERSON] and [PERSON] [16] surveyed, keeping efficient energy routing for UWSN in mind. They proposed a new taxonomy and did a comprehensive survey of energy-efficient routing protocol schemes. Nevertheless, they only surveyed extensively on the energy-efficient part of the protocols and not the other two categories described earlier in the paper. In differentiation to this paper, we provide a detailed overview of all three types of protocols which will provide readers with ample information to choose the right network for their work. * [PERSON] et al. [17] surveyed state-of-the-art routing protocols for UWSNs but they surveyed protocols of the past two years and a few classic protocols. They classified the protocols into three categories; energy-based, geographical information-based, and data-based. Similarly, our work considers the same three categories. However, our work also considers protocols before 2018, this gives readers an idea of the differences in architecture and the novelty and drawbacks of the protocols. * [PERSON] et al. [18] surveyed seven different kinds of intelligent protocols and classified them into two main categories, cross-layer and non-cross layer. They further categorized the cross-layer into two subcategories: intelligent algorithm and traditional cross-layer protocol, and the non-cross layer into mobility-based, energy-efficient, and time-delay-based protocols. However, they did not mention the route-choosing processof the protocols, which is discussed in our paper. We also discuss the key ideas and drawbacks of the protocols. * [PERSON] et al. [19] did a comprehensive survey on the application of UWSN. They classified the uses into five categories: monitoring the water condition, disaster management, distress signals, military uses, assisted navigation, and sports. They explained the taxonomy and used UWSN for three of the five categories. They described the communication architecture of the sensors. However, they did not mention the path propagation choice of the sensors. In contrast to this paper, our paper focuses on the routing protocol for the user to better understand how the data is transferred from the sink node to the base station. * [PERSON] et al. [20] proposed an extension of UWSN with the addition of Internet of Things(IoT) in the UWSN network. They proposed dividing the system's architecture into two types: underwater and non-underwater. The two parts consist of five layers: sensing, communication, networking, fusion, and application. However, they did not talk about any specific routing protocols that can be used. They focus more on the future opportunities of the Underwater Internet of Things (UIoT) and the differences it can make. * [PERSON] et al. [21] focused on the routing protocols for UWSN. They classified the protocols into two categories, sender-based and receiver-based. They classified both into three subgroups: energy-based routing, geographic information-based routing, and hybrid routing. However, unlike our study, they compared very few protocols, whereas we give a comprehensive study of underwater wireless sensor networks.