## 1 Introduction
[19] proposed UCMAC protocol which is an underwater cooperative MAC protocol for UWSNs as a reactive type. [PERSON] et al. [20] proposed an asymmetric propagation delay-aware time division multiple access protocol for mobile acoustic UWSNs requiring periodic transmission of data. [PERSON] et al. [21] proposed a dual channel MAC protocol for acoustic UWSNs where each node uses two underwater acoustic antennas that one is directional and the other is omnidirectional. [PERSON] and [PERSON] [22] proposed a handshake-competition MAC protocol with a power control for underwater acoustic networks. [PERSON] et al. [23] proposed a dynamic timeslot contention MAC protocol based on predicting positions of autonomous underwater vehicles (AUVs). [PERSON] et al. [24] proposed an underwater multi-channel MAC protocol which is based on underwater localization and a single transceiver. A two-dimensional discrete Markov chain is presented to model the back-off mechanism. The underwater localization is based on the time difference of arrival (TDoA) that may not need time synchronization. In UWSNs, underwater localization can be an important issue and there have been many studies on underwater localization techniques. [PERSON] et al. [25] presented a review of localization techniques for acoustic UWSNs. Underwater localization techniques can belong to distributed localization or centralized localization. They can also fall into prediction-based localization or estimated localization. The received signal strength indicator, the time of arrival (ToA), TDoA, and the angle of arrival can be used for underwater localization techniques. [PERSON] et al. [26] proposed a localization approach for mobile nodes in acoustic UWSNs. The localization approach utilizes a Kalman filter to align the timestamps received from neighboring anchor nodes. Since the localization approach also utilizes a penalty convex-concave procedure and sound ray tracing, the lake experiment and the deep sea experiment show that the localization error for the mobile node can be reduced. [PERSON] et al. [27] presented a method to optimize the formation of AUVs for three-dimensional cooperative localization of AUVs. Since the method utilizes the measurements of TDoA, the method can reduce the localization error by increasing the information related to TDoA. [PERSON] et al. [28] proposed a mobility-assisted localization scheme that can be suitable for three-dimensional large-scale UWSNs. The localization scheme considers the measurement of distance between sensor nodes that does not need time synchronization. The localization scheme utilizes two-way ToA for the localization of the remaining sensor nodes. For UWSNs, there have been many studies on other issues including resource allocation and routing protocols. [PERSON] et al. [29] proposed resource allocation algorithms for the downlink of an acoustic UWSN that consists of underwater sensor nodes, buoy nodes, and a base station on a ship. They consider that the buoy node can act as a relay and harvest the energy. In the downlink of an acoustic UWSN, one resource allocation algorithm is presented to maximize the sum rate and another resource allocation algorithm is presented to maximize the energy efficiency. [PERSON] et al. [30] proposed a geographic and opportunistic routing protocol for a UWSN that consists of underwater sensor nodes, surface sonobuoys, and a monitoring center. The routing protocol can route a data packet from an underwater sensor node to some surface sonobuoys using the anycast nature. It is assumed that if a surface sonobuoy receives a data packet, it can forward the data packet to a monitoring center. The routing protocol utilizes a periodic beaconing algorithm, a next-hop forwarder set selection algorithm, and a void node recovery algorithm. Since each underwater sensor node is assumed to know its own location, the location of neighbor nodes can be disseminated via the periodic beaconing algorithm. [PERSON] et al.