## 2 Related Word
### Localization Free Routing Protocols
In EVAGR [37], a weighted function is applied for the selection of the best sending node. The weighted function is based on the three parameters i.e., potential neighbor node selection, depth value of the potential neighboring nodes, and their remaining energy information. The best neighbor node is chosen based on packet progress to the void spot, and initial packets are sent to network nodes. In EE-LCHR [38], a layered-based clustering routing protocol is presented where the whole network region is subdivided into multiple layers. All layers consist of a similar number of acoustic nodes deployed. The k-means technique is used to form clusters in individual layers. The cluster head is picked based on fitness value. The data transmission is based on the depth and distance parameters of the nearest neighboring cluster head. To conclude, the reviewed protocols as shown in Table 1, utilize a random deployment technique which opens up a research gap in addressing the void hole issue. Furthermore, the path selection criteria are predominantly based on energy levels, link quality, or the availability of neighboring nodes. This presents an opportunity to enhance network performance, particularly in terms of energy efficiency and communication reliability. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Protocol** & **Descriptions** & **Deployment Technique** & **Merits** & **Demerits** \\ \hline \multirow{3}{*}{EECMR [12]} & The duration of CH is & \multirow{3}{*}{Random and sparse parameters of CH. The nodes in between layers act as relays} & \multirow{3}{*}{Improved energy consumption} & Random and sparse deployment increases the chances of void region \\ \cline{1-1}  & The duration of CH is & & & \\ \cline{1-1}  & considered as the selection & & & \\ \cline{1-1}  & parameters of CH. The nodes & & & \\ \cline{1-1}  & in between layers act as relays & & & \\ \hline \multirow{3}{*}{GEDAR [27]} & Geo-opportunistic routing & Random & \multirow{3}{*}{Improved PDR} & High energy consumption, increased E2 ED \\ \cline{1-1}  & based on depth adjustment & & & \\ \hline \multirow{3}{*}{DBR [28]} & Use a greedy strategy, to & \multirow{3}{*}{Random deployment} & Improved energy utilization and PDR & Not considered void handling, high E2 ED, more energy consumption \\ \cline{1-1}  & efficiently manage the & & & \\ \cline{1-1}  & dynamic network & & & \\ \hline \multirow{3}{*}{HydroCast [29]} & Pressure-based & \multirow{3}{*}{Random deployment} & Efficiently handles void issues, Improved PDR & High energy consumption \\ \cline{1-1}  & routing protocol & & & \\ \hline \multirow{3}{*}{LLSR [30]} & Hop-based routing protocol, & \multirow{3}{*}{Random deployment} & \multirow{3}{*}{Decreased E2 ED} & Increased energy consumption and communication overhead \\ \cline{1-1}  & void nodes can be identified by & & & \\ \cline{1-1}  & the beaconing technique & & & \\ \hline \multirow{3}{*}{IVAR [31]} & Beacon containing hop count & \multirow{3}{*}{Random deployment} & \multirow{3}{*}{Decreased E2 ED, high PDR} & High energy consumption due to duplicate packet transmission \\ \cline{1-1}  & and depth value based on & & & \\ \cline{1-1}  & greedy forwarding approach & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Related works in existing UASN routing protocols.