## 1 Introduction  
The deployment of UWSNs (Underwater Sensor Networks) requires a large number of tools and sensors which are located in a specific area for monitoring. According to [1], due to sea currents, the movement at underwater sensor networks is usually 2-3 m/s. So, it is required great attention from the designer in order to apply data communication techniques and protocols as efficiently as possible. The acoustic waves are widely used in underwater communication systems due to their low absorption in aquatic environments, where radio or optical waves cannot sufficiently propagate [2]. The ocean sea can be generally divided into shallow area and deep zone, whose basic distinguishing features are generally [1]:  
- depth (0-100 m for the shallow area and up to 10 km for deep area),  
- temperature (at shallow areas may have fluctuations and assumes usually relatively high values, while in very deep areas it reaches constant low value),  
- scattering factor (cylindrical for shallow and spherical for deep areas). The shallow areas greatly influence the acoustic channel due to its large gradient temperature, salinity variations and the effect of multipath due to surface and bottom reflections. All these variations bring changes in the network that can be used to monitor. There are various survey studies that give a full detail report about the available methodologies for the channel utilization, impact of environment factors, localization of nodes, routing protocols and the effect of packet size on communication [1]. While others are focused on the estimation of simulation tools and testbeds [3], as their implementation is still expensive. An accurate simulation model for sure can help to create an approximation of the behavior of UWSNs in a real scenario. This helps to highlight new directions of research for further improvement in UWSNs. That is why we have simulated different distribution of link failures for DEADS (Depth and Energy Aware Dominating Set Based Algorithm) routing algorithm at [4]. It is important to find out how missing links will influence the network lifetime and residual energy of network, because the right chosen of node degree can help specially when the energy of network is going down. Another physical element that influences the node degree, is the mobility of the nodes [5]. There are compared two different kinds of networks: one with settled positioning of the nodes from the beginning of the simulation and the other where the nodes change their position during the simulation. In the second case, the distances change any time, nodes move to different random positions and the network is on a continuous change of topology and nodes role. Due to the harsh environment, the conditions of network are not stable, that is why again is estimated also the presence of link failures. The results bring to the conclusion that where the nodes move due to water flow then node degree can diminish with time, that means that the network is less connected. The energy also in this case still is less because few nodes are active. This study helps to have the results of the network that keeps changing and shows the results of the calculated residual energy in the network, that is very important for the lifetime of a network that needs to monitor such difficult environment. After that we studied the impact of intermittent noises in the range of acoustic modem communication [6]. As we saw intermittent noises, when presented they have a significant impact on decreasing the transmission range. The calculations made for the parameters of the modem Evologics S2 CR7/17 showed that for the oceanic environment with the minimum received noise level, the range of communication is depending on the frequency from 9634 m to 4286 m, or on average 6414 m. Our calculations for the impact of intermittent noise showed that this transmission range may, in certain conditions, decrease considerably. According to [PERSON]'s lines, we calculated the maximum relative distances that this modem is capable to transmit.