###### Abstract  
After the occurrence of a maritime disaster, to save human life and search for important property equipment in the first time, it is indispensable to efficiently transmit search and rescue sea area data to the maritime search and rescue command center (MSRCC) in real-time, so that the MSRCC can make timely and accurate decisions. The key to determining the efficiency of data forwarding is the quality of the routing protocol. Due to the high dynamics of the marine environment and the limited energy of the marine node, the coverage hole and routing path failure problems occur frequently when using the existing routing algorithm for marine data forwarding. Based on the above background, in this work, we study a low-latency and energy-efficient opportunistic routing protocol for maritime search and rescue wireless sensor networks (MSR-WSNs). Considering the adverse impact of wave shadowing on signal transmission, an effective link reliability prediction method is first investigated to quantify the link connectivity among nodes. To mitigate the end-to-end time delay, an optimal expected packet advancement is then derived by combining link connectivity with geographic progress threshold \(\theta\). After that, based on the link connectivity between marine nodes, the optimal expected packet advancement prediction, the distance from the sensing nodes to the sink, and the remaining energy distribution of the nodes, the priority of candidate nodes is calculated and sorted in descending order. Finally, timer-based coordination algorithm is adopted to perform the marine data packet forwarding so as to avoid packet conflict. Computer simulation results demonstrate that compared with benchmark algorithms, the data packet delivery ratio, the delay performance and the average node energy consumption (the average node speed is 20 m/s) of the proposed opportunistic routing protocol are improved by more than 21.4%, 39.2% and 18.1%, respectively. m 27 September 2022 27 October 20  
the capability of the traditional terrestrial routing methods, and (3) limited energy for sensor nodes. Numerous research has been investigated in terms of routing protocol in WSNs with mobile nodes [6; 7; 8; 9; 10; 11; 12; 13; 14; 15]. To name a few. To reduce the network energy consumption, [PERSON] et al. [6] presented a Q-learning-based localization-free any path routing protocol for underwater WSNs, which effectively prolongs the lifespan and reduces the end-to-end delay. In [8], an Energy-Efficient and Reliable Routing protocol was presented for mobile WSNs that minimized routing overhead and overcame unreliable communication links. [PERSON] and [PERSON] [14] presents Mobile Energy Aware Cluster Based Multi-hop (MEACBM) routing protocol, which introduces mobile nodes as Mobile Data Collector (MDC) to collect Cluster Heads data and transmit it to the Base Station. Unfortunately, none of the above protocols comprehensively consider the end-to-end performance and the characteristics of marine environment, so they are not suitable for highly dynamic MSR-WSNs. It needs to be emphasized that the MSR-WSNs studied in this paper is a more dynamic sea surface wireless sensor networks than underwater WSNs, and the communication technology used between nodes is radio signal propagation. In contrast with traditional routing algorithms, opportunistic routing could significantly reduce packet retransmission due to link failure by dynamically selecting forwarders from multiple candidate neighboring nodes [15]. The next-hop used for the data packet forwarding depends on which forwarding nodes receive the packet and the priority order of candidate nodes [16]. Therefore, opportunistic routing can better adapt to the unstable and dynamic networks. In recent years, some scholars have also carried out some research on the opportunistic routing protocol design of marine sensor networks [17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. To name a few, [PERSON] et al.