## 1 Introduction  
With the development of modern science and technology, human beings are more and more fully aware of the use and development of the environment, and the ocean, due to its rich resource reserves and research value, has prompted us to continuously explore the underwater space. The sensor nodes suitable for the underwater environment are deployed in the underwater environment for resource exploration, disaster prevention, data collection and other works. The sensor node forms a highly flexible underwater wireless sensor network (UWSN) through underwater acoustic communication. UWSN can be classified according to different standards: one is divided into static, semi-static and dynamic networks according to node mobility; another common classification is divided into 2D and 3D topologies structures according to whether the depth of nodes is considered [1]. In the common 2D UWSN structure, nodes are usually placed on the seabed [2]. Due to the special underwater environment, sensor nodes are small in size [3]. Unlike radio wave transmission, underwater signals can only be transmitted through sound channels, which will affect the communication quality [4]. In the 3D structure, nodes are distributed at different depths in the water to conduct comprehensive monitoring of the water area [5]. The depth of the sensor nodes can be controlled by buoys fixed on a horizontal plane [6]. The 3D network structure can more intuitively reflect the monitoring environment of underwater sensors [7]. However, the challenges of this structure involve nodes positioning and ensuring that all areas are continuously covered [8; 9]. It is meaningless not to know the monitoring data of node location and if the area coverage is low, its application value will be affected. In addition, a good coverage method can also play a role in reducing the total cost [10]. Because the coverage of a single node is much smaller than that of target monitoring, many nodes must cooperate to achieve full target coverage [11]. Many algorithms optimize the coverage of the network from different angles [12], but this goal is still difficult to achieve, because the speed of water, the creatures in the water and the passing ships may destroy the placed nodes, thus affecting normal communication [13; 14]. How to ensure network coverage in a complex underwater environment is a reliable and complete guarantee for UWSNs monitoring and collecting data. The UWSNs sensor nodes are battery-powered and are often difficult to replace [15]. Network performance will be affected once the node energy is exhausted and the cover hole occurs [16]. Topology control enables the network to eliminate unnecessary communication links between nodes, equalize the energy of nodes in the network, and prolong the network lifetime on the premise of satisfying coverage and connectivity. Generally speaking, topology control mainly consists of topology structure and topology maintenance, and is one of the effective solutions to save energy and prolong lifetime [17]. By selecting the appropriate cluster head for the topology control of nodes in the network, the effect of balancing network energy consumption can be achieved [18]. The common topology control method is to set the sleep node [19]. In this paper, nodes distributed in water are divided into clusters, control nodes in the cluster are changed according to the residual energy of nodes, and the dormancy time of nodes is set in combination with the number of neighbors, so as to reduce network energy consumption and prolong network lifetime [20]. Based on the above background, this paper designs a cluster sleep-wake scheduling algorithm based on 3D topology control. The algorithm achieves high network coverage and connectivity, and the clustering and sleep-wake strategies greatly prolong the network lifetime. The rest of this paper is organized as follows. Section 2 explains relevant research results on UWSNs and analyzes network energy consumption and coverage defects. Section 3 proposes a network model for UWSNs.