## 1 Introduction  
Over the past ten years, interest in underwater wireless sensor networks (UWSNs) has grown significantly [1]. Due to the seas and water that cover it, the earth is known as the \"blue planet\" in the solar system [2]. Since the oceans cover more than 70% of our world [3, 4], UWSNs are extremely important and an important research area [5]. Exploration underwater has increased significantly in the recent past [6]. UWSNs are made up of sensor nodes, and these nodes exchange data and communicate [7]. These sensor nodes have limited battery capacity [8]. In UWSNs, the sensor nodes also communicate with one another to determine the optimum path based on a set of criteria. The data are transmitted using the best route possible from the bottom of the sea to the surface level of the water, and then further [9, 10, 11, 12]. UWSNs have the potential to explore hidden underwater resources. Additionally, they have enhanced capacity for both prediction and observation of the oceans [13]. Other significant UWSNs endeavors include ocean resource exploration, underwater information exchange, monitoring, and disaster avoidance [9, 10, 11, 12, 14, 15]. Due to the constrained context of UWSNs, they are very different from conventional WSNs. Furthermore, compared to the context of WSNs, the issues faced by UWSNs are very different [16]. The major challenge in WSNs environment is the smaller battery power capacity of the nodes [17]. Some important research contributions in ad-hoc and sensor networks include improving fault tolerance [18], detection of faulty nodes in WSNs [19; 20], reliable data transfer protocol for WSNs [21] and routing approach in IoT [22]. Due to a variety of factors, communication in the UWSNs context is difficult and unpredictable [23]. Due to absorption, high-level attenuation, and dispersion, radio waves in UWSNs are not effective. The atmosphere of UWSNs is suitable for the transfer of data via acoustic communication [24]. The range of frequencies that can be used for acoustic waves is limited, which affects their applicability in underwater communication [25]. In contrast to radio communication, where the speed of transmission is the same as the speed of light, the speed of propagation for acoustic communication is slower, i.e., five times slower than radio waves. The end-to-end and propagation delay in acoustic communication in UWSNs is greater due to the slower propagation speed of 1500 m/s. The usable bandwidth for audio communication is under 100 kHz. While most sensors in UWSNs are stationary, they can still move at a speed of 1 to 3 m/sec [16; 26; 27; 28; 29]. Figure 1 shows the UWSNs architecture. The sensor nodes deployed in UWSNs environment are labeled as sensor node A, B... O and these nodes communicate under the water via acoustic waves. Since the nodes utilized in UWSNs are operated by battery and rely on their remaining energy to function, maximum research in UWSNs focused on energy efficiency. Energy efficiency and security are equally important in the context of UWSNs. This research project, therefore, focuses on the effects of a security breach in a routing protocol in the context of UWSNs. The well-known routing system AMCTD [30] provides an effective routing solution for UWSNs environment. In order to investigate the effects of a security breach in a well-known routing system, this study actively attacked the AMCTD protocol. With the help of this work, the research community will better understand the effects of attacks in the UWSNs and will take required measures into account while building routing protocols for the UWSNs environment. The rest of the research article is structured as follows: Related work is discussed in Section 2; Details regarding the AMCTD protocol are presented in Section 3; An active attack in the AMCTD protocol is discussed in Section 4; Performance evaluation and simulation parameters are mentioned in Section 5; Results are presented and discussed in Section 6; and the research is concluded in Section 7.