## 2 Related Work  
There is growing literature about medium-access strategies to improve energy efficiency in underwater wireless sensor networks. In wireless sensor networks, the aim of MAC protocols is to decrease latency in the network and focus on the management of high traffic, which is extensively studied [19]. These efforts can be categorized as contention-based and contention-free protocols. In contention-based protocols, all nodes can transmit data packets simultaneously without any predefined scheduling algorithm. In [20], a contention-based MAC protocol, TDTSPC-MAC, is developed for three-dimensional UASNs facing challenges such as long propagation time, high bit error rate, and limited bandwidth. The protocol integrates time synchronization, power control, clustering, layering, and sleep mechanisms. TDTSPC-MAC utilizes hierarchical division of three-dimensional space and a distributed clustering algorithm, combining time synchronization and power control strategies to prevent collisions and reduce energy consumption through monitoring and sleep mode. Yet, in scenarios involving extensive data transmission or a significant number of nodes, data packets become susceptible to collisions. Large transmission delays and limited transmission rates inherent in underwater sensor networks increase collision probability and cause low energy utilization. In [21], a delayed-reward ALOHA-Q protocol is designed for UASNs. By leveraging Q-learning, DR-ALOHA-Q autonomously determines optimal time slots and offsets for data transmissions to improve channel utilization in the presence of large propagation delays. Contention-based methods require active listening and short control packet exchanges in order to mitigate long idle waiting times and improve overall energy consumption and transmission delay in UASNs. In [22], challenges in underwater sensor networks related to high latency, low bandwidth, and high bit error rate in acoustic communication are investigated. It highlights the limitations of contention-based medium access control (MAC) protocols in UASNs and proposes a novel contention-free MAC protocol called DL-MAC. The DL-MAC protocol addresses underwater MAC challenges through depth-based layering, a distributed clustering algorithm, and TDMA-based scheduling, demonstrating superior performance in terms of throughput, packet delivery ratio, energy consumption, and packet loss. On the other hand, contention-free MAC protocols can easily address the well-known hidden node problem without extra control packet overhead and interference of neighboring nodes by utilizing scheduling nodes to distinct time slots to perform transmissions. A well-known contention-free MAC protocol, TDMA, attracted researchers, while other contention-free protocols, such as FDMA, suffer from limited available bandwidth, and CDMA faces challenges due to the near-far problem [23]. Hence, TDMA-based MAC protocols have been the main focus for long-term surveillance applications in the literature. Numerous TDMA-based medium access methods are proposed [24; 25; 26] to leverage the benefits of simplicity, fairness, and energy efficiency by mitigating issues such as collisions, idle listening, and transmission over-hearing. However, TDMA-based MAC protocols exhibit certain drawbacks, such as suboptimal channel utilization, challenges in dynamic scalability, and the need for time synchronization. [PERSON] et al. [27] proposed an online scheduling algorithm to calculate the optimal action, namely, the decision of transmitting the packet or holding it back in the packet queue in each time slot, with the aim of decreasing energy consumption in packet transmission. In this work, a channel state prediction algorithm is employed in order to determine the optimal action. Aiming to minimize energy consumption and considering the channel conditions in transmissions, a transmission strategy is proposed in [28]. Ref.