## 4 USWN Applications  
The USWN, a UWC technology, is a network of autonomous sensor nodes [5; 21; 60]. It combines smart sensing, intelligence computing, and communication capabilities, enabling underwater scientific and commercial explorations, coastline protection, pollution monitoring, water-based disaster prevention, and water-based recreational activities [21]. Considering that numerous resources lie underwater, UWSNs make it possible the explorations of underwater environments that were recently inaccessible [21; 60]. Several applications are found for UWSNs besides in mineralogy [21; 60]. USWN technologies are implemented in the monitoring of marine, riverine, and lacustrine lifeforms, as well as the conditions of these environments [21; 60]. Sensing turbidity, temperature, density, pressure, water currents and quality, conductivity, pollutants, object tracking, ecosystem modelling, and species classification are some of the key functions made possible by UWSNs [21; 60]. In a USWN, a set of nodes transfer their data to buoyant nodes known as gateways that relay the data to the nearest remote station, a coastal monitoring and control station [21]. In UWSNs, sensor nodes are classified as static or stationary and mobile [5; 21; 60]. Table 8 lists the types of UWSNs and their applications and constraints. A combination of the two classes can be implemented in the same sensor network fulfilling distinct requirements, such as transferring various events of interest [21; 60]. [PERSON] et al. [7] applied a sensor network comprised of node-to-node high-speed optical communication with the aim of monitoring corals and reefs. The experimentation has been conducted in pools, rivers, and oceans [7]. They incorporated acoustic protocols into the TinyOS stack to broadcast the network. The nodal points are equipped with various types of sensors to capture pressure, temperature videos, and images [5; 7; 21]. The mobility of the mobile nodes is used for locating and hovering over static nodes for \"data muling\" and other maintenance tasks such as recovery, deployment, and relocation [7]. Various USWN architectures are implemented, namely One-Dimensional (1D), Two-Dimensional (2D), Three-Dimensional (3D), and Four-Dimensional (4D) [21]. These four architectures reflect the way data are conveyed from underwater sensing to reception at \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Sensor Network Type** & **Applications** & **Challenges** \\ \hline \multirow{4}{*}{Static Sensor Networks} & Monitoring water quality, & \\  & turbidity, temperature, density, pressure, currents, pollutants, and ecosystems. & Power consumption, deployment, maintenance \\ \hline \multirow{4}{*}{Mobile Sensor Networks} & Object tracking, species & \\  & classification, data muling, recovery, deployment, and relocation. & Power consumption, mobility limitations \\ \hline Hybrid Sensor Networks (Static and Mobile) & Combines the advantages of both types. & Power consumption, coordination \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Sensor networks modalities and applications [21; 98]. the remote station [21]. The 1D-USWN architecture is characterized by a star topology, and transmission of data from a stand-alone sensor node to a remote node is accomplished in a single hop [21]. An example of a 1D-USWN is the application of AUVs which dive underwater, sense and retrieve data, and relay to the remote station [21]. The deployment of 1D-UWSNs is autonomous and each node is a stand-alone network itself, tasked to sense, process, and transmit data to the remote station [21]. The 1D-UWSN architecture can be as simple as a floting buoy capable of sensing underwater properties and can use UWOC, UWAC, or RF communication systems [21]. The 2D-USWN architecture features a cluster of nodes, including one which is the anchor node or cluster head, which is responsible for gathering the data or information from every sensor node in the cluster and sending them to the buoyant gateway node.