I.J. Wireless and Microwave Technologies, 2020, 4, 22-33 Published Online August 2020 in MECS (http://www.mecs-press.org/) DOI: 10.5815/ijwmt.2020.04.03 Copyright © 2020 MECS I.J. Wireless and Microwave Technologies, 2020, 4, 22-33 Sagacious Communication Link Selection Mechanism for Underwater Wireless Sensors Network Shahzad Ashraf *1 , Sehrish Saleem 2 , Tauqeer Ahmed 1 1 College of Internet of Things Engineering, Hohai University, Changzhou Jiangsu, China 2 Muhammad Nawaz Sharif University of Engineering & Technology Multan Pakistan Email: nfc.iet@hotmail.com Received: 06 April 2020; Accepted: 13 May 2020; Published: 08 August 2020 Abstract: In underwater environment, the sensor nodes are deployed for collecting information and sending back to the base station. Establishing astute communication link among these sensor nodes in a multi-link routing environment is a key challenge for all underwater routing protocols. A sagacious communication link can only guarantee the maximum data transfer rate. The link selection mechanism of three underwater routing protocol i.e, Energy-aware Opportunistic Routing (EnOR) protocol, Shrewd Underwater Routing Synergy using Porous Energy Shell (SURS-PES) and Underwater Shrewd Packet Flooding Mechanism (USPF) have been investigated. After analyzing performance results of these protocols interms of packet delivery ratio, end-to-end delay, network lifespan and energy consumption using NS2 with AquaSim 2.0 simulator. The protocol existing, with sagacious link selection mechanism in multi-link routing environment has been identified. The identification of this sagacious link selection mechanism is a novel approach which can give specific knowledge for targeted output without wasting resources for irrelevant objectives. Index Terms: Flooding mechanism, underwater routing, link selection, sagacious link, sink node 1. Introduction Rummaging for oceanic resource, the underwater wireless sensor network plays a demanding role in this regard. It encompasses different varieties of sensor nodes according to the aquatic environment and meet the sensing data objectives. The deployed sensor nodes are fabricated with Radio Frequency (RF) and acoustic modem, used for sensing data related to atmosphere and unusual activities for instance, ocean and river pollution discovery, oil-and- gas exploration, battlefield spying, building inspection, target-field imaging, disaster detection-and prevention, submarine-targeting, detection-of atmospheric-conditions such-as change-in temperature,-light, sound-or the-existence of-unlikely objects [1]. The sonobuoys (sinks) nodes float at upper water-surface and-responsible for-collecting related data-from these nodes. The-underwater sensor network is only feasible with acoustic channel. The acoustic signals operate at 1500-m/s which is less than the electromagnetic wave frequency in five order magnitudes [2]. The performance of the underwater network depends heavily on the topology architectural style, that is controlled by a selection mechanism for perfect embodiment deployed nodes which improves the probability of transmission to the destination node. There are numerous challenges hindering to UWSN, the low bandwidth with absurdly high channel error rate, the transient route failure and weak channel multipaths, continue node displacement by 2-3-m/s at-water current [3]. Sound speed-is viewed stable-in the underwater-environment. However, sound intensity is influenced by the temperature, depth and salinity of the underwater ecosystem. These influences cause fluctuations in sound intensity in the underwater environment [4]. Underwater acoustic channel frequency range, particularly in mid-frequencies, is commonly shared by different acoustic users in underwater environments. Foremost, UWSN is facing an exorbitant energy wastage problem, all nodes are battery dependent and no mechanism has explored yet for replacement or charging. Therefore, in order to confine the energy wastage and utilizing the batteries potency efficiently, it is the only way to design a shrewd underwater routing protocols that should select the best and shorted rout between source and destination node [5]. The traditional terrestrial routing protocols are not well fitted in underwater environment. The optical and radio frequency interactions in such networks are generally deemed infeasible because optical signals suffer from extreme interference, while high-energy radio signals are easily absorbed due to high attenuation [6]. Establishing a communication link among deployed underwater nodes is major task of every underwater routing protocol and indeed it is a backbone of the routing mechanism. An underwater sensor network operates in multi-hop environment and thereby