## 1 Introduction  
Many applications are associated with underwater environments such as surveillance, ocean monitoring, and disaster mitigation to measure the level of the sea due to the melting process of ice. Acoustic communication is the process of receiving and sending messages by using sound waves in an underwater environment. The underwater architecture usually consists of sensors and vehicles that deploy in some area of the seafloor to record the data at a fixed location. The collection of underwater information can be possible due to randomly placed underwater sensors that collect some important hydrologic data for example pressure, temperature, and salinity. However, it is important to recover these deployed sensors after the completion of the task. Underwater sensor nodes are mostly in moving positions because of the sea flow and other creatures after their deployment. It is very important in many applications that the location of sensors is known, otherwise, the collected information is meaningless and since the localization is depending upon synchronization then it is very useful to perform both localization and time synchronization within the same scenario. The major disadvantage of traditional local approaches is a lack of communication, and the recorded data could be destroyed in the case of any failure. A wide variety of applications are supported by underwater sensors such as river and sea pollution discovery, aquatic surveillance, monitoring, commercial exploit the aquatic environment oceanographic data. UWSNs applications require two types of services which are depending upon each other. For example, time division multiple access (TDMA) is an important medium access control (MAC) protocol that often requires accurate time synchronization between sensor nodes. The information exchange process about the local clock drift is the most common procedure in UWSNs. An accurate localization technique is required to monitor the underwater surroundings because the collected information is only beneficial if the nodes are localized up to certain accuracy, otherwise, the gathered information is meaningless. Localization is also very important for surveillance applications. Long-range missions can be possibly done by long endurance \"autonomous underwater vehicle\" AUVs, for example, underwater gliders which are energy efficient. These vessels mostly spend their time navigating along a straight course which is controlled by an inertial navigation system or electronic compass during this whole long-term mission. However, these underwater gliders don't aware of their position and path that make them affected by ocean currents and waves. Today, we use such vehicles which are the only autonomous underwater platforms that can collect the ocean information without any local assistance for several months. Hence, they are considered a powerful tool for the improvement of ocean knowledge. Like localization, synchronization is a fundamental problem in distributed sensor networks especially since the timestamp is an important factor while sensing the data. Furthermore, underwater sensor nodes have limited energy resources, which has a substantial impact on the lifetime of the network. Therefore, an energy self-sufficient UWSN is essential to maximize the lifetime of the network. In comparison with traditional wireless sensor networks (WSN), the underwater environment is based on anchor nodes with known locations and synchronized clock, also, there are ordinary nodes whose location is unknown, and their clocks need to be synchronized. The process of finding the location and synchronization is mainly associated with message exchange between sensors and anchor nodes, but in most cases, are handled separately [1; 2]. Because it was initially assumed for underwater localization, that all acoustic signals travel with the speed of 1500 m/s, due to this, methods like [3] provide a high estimation error. However, later, this error was improved by taking the fact that sound speed should be considered as an unknown perimeter.