## 2 Background
### Internet of Underwater Things (IoUT)  
Nowadays, technological innovations allow millions of devices to connect to the global network. This industrial revolution was described by the term IoT (Internet of Things) and was led by the need of users to be constantly connected to their devices to conduct daily activities [14]. The IoT supports a'smarter' way of living, assisting daily tasks and our wellbeing, such as home automation. Regarding the underwater (sea) \"world\", there were various daily tasks which could be facilitated, and numerous devices of underwater vehicles needed to interoperate in an underwater sensor network (UWSN) or underwater wireless communication network (UWCN) [15]. Sea species tracking, maritime security and naval military activities and gas/oil extraction are some of these activities. The Internet of Underwater Things (IoUT) has been introduced, not necessarily to simplify such tasks, but to support the efficient interconnection of underwater vehicles, devices, and sensors to the Cloud. The IoUT has brought new research and development directions in a new ecosystem which facilitates the connection of assets \"living\" underwater and on the sea surface. It aims to tackle several challenges of UUVs such as interoperability, data management, and secure communications, contributing to the development of research, business and underwater military or civil operations [15]. In such an ecosystem, there is a need to establish a fault tolerance connection between underwater and surface assets, meeting key requirements such as heterogeneity, network coverage, low latency, low power usage or battery efficiency, and cyberattacks. The IoUT must integrate heterogeneous assets, to be able to interoperate effectively in UWCNs and UWSNs. Specifically, a UWSN has its own requirements (longevity, accessibility, complexity, security, and environmental sustainability), and the need for a taxonomy based on specific key attributes, such as architectural elements, communication, routing protocol, security, and applications [16]. The establishment of a robust and secure underwater ecosystem is a continuous process as the threats to be countered are becoming more and more sophisticated. IoUT has certain similarities to IoT such as its structure, function, and its energy limitation. However, a few differences exist, which are related mainly to the heterogeneity of assets in terms of their: (a) communication technologies, (b) tracking technologies, (c) low battery capacity and difficulty of recharge, (d) energy harvesting technologies, (e) network density, (f) localization techniques [17]. Therefore, as mentioned in [18], in order to successfully establish a UWCN/UWSN, and obtain IoUT capabilities, at least the following issues must be considered: (a) the communication medium, i.e., the water, (b) the dynamic changes of network topology, (c) the energy consumption and maintenance constraints, (d) the hazardous environment and physical security, and (e) localization [18]. Limited bandwidth, transmission media (acoustic communication) and low propagation speed of IoUT, in combination with the volume of data to be transmitted, as in IoT, lead to delays in information distribution. This fact allows cyber-adversaries to remain further undetected and achieve their goal efficiently. More specifically, slow transmission rates has consequences of the delayed evaluation of an alert and the delayed reaction to a cyberattack. A way to deal with limited bandwidth and delay in underwater communications and environmental and ambient noise [19] on a communications channel, is the development of data analysis software to optimize the process. Such a method is proposed in [20], to balance data traffic loading in an underwater network and minimize latency issues. This is conducted by presenting intelligent data analytics (IDA), which support high packet allocation in combination with low latency and less energy consumption.