50 Int. J. Ad Hoc and Ubiquitous Computing, Vol. 29, Nos. 1/2, 2018 Copyright © 2018 Inderscience Enterprises Ltd. Spider monkey optimisation based energy efficient clustering in heterogeneous underwater wireless sensor networks Madhuri Rao* Department of Computer Science, Siksha ‘O’ Anusandhan University, Bhubaneswar, Odisha, 751030, India Email: madhurirao@soa.ac.in *Corresponding author Narendra Kumar Kamila Department of Computer Science, C.V. Raman College of Engineering, Bhubaneswar, Odisha, India Email: nkamila@rediffmail.com Abstract: Multi-hop propagation is not viable in Underwater Wireless Sensor Network that uses acoustic signals. It causes more energy drainage of the network nodes due to longer delays in signal propagation. Also, UWSN is prone to dynamic topology changes due to node mobility caused by water current. It leads to transmission errors, link loss, collisions and congestion, if not well handled. A clustering approach based on spider monkey optimisation (SMO) is proposed here that addresses these issues. The proposed approach is found to enhance the average network lifetime of nodes by 0.01579 J and achieves a network gain of 1.35%. Further a significant reduction in average delay of messaging packets by 19.82% is achieved. The proposed approach is far more optimised as it reduces the average hops between sender and receiver by 20%. Keywords: heterogeneous underwater wireless sensor networks; dynamic clusters; SMO; spider monkey optimisation; FFSS; fission–fusion social structure. Reference to this paper should be made as follows: Rao, M. and Kamila, N.K. (2018) ‘Spider monkey optimisation based energy efficient clustering in heterogeneous underwater wireless sensor networks’, Int. J. Ad Hoc and Ubiquitous Computing, Vol. 29, Nos. 1/2, pp.50–63. Biographical notes: Madhuri Rao is an Assistant Professor in the Department of CSE at Siksha ‘O’ Anusandhan University. She received her post graduation degree in Master of Technology from Bharath University, Chennai. Her recent publication is ‘Tracking an Intruder Ship in Wireless Environment’. Her research interests include mobile computing, ad-hoc networks and distributed systems. Narendra Kumar Kamila received his Master degree from Indian Institute of Technology, Kharagpur and subsequently obtained his PhD from Utkal University, Bhubaneswar in 2000. He was also Post Doctoral Fellow to University of Arkansas, USA. He has completed many projects sponsored by various sponsoring agencies. He has guided many MTech and PhD students. His research area includes wireless sensor networking, ad hoc networking; image processing, meta cognition and data privacy/security. 1 Introduction Underwater wireless sensor network (UWSN) is being used for study of marine life (Odegard et al., 2016), harbour surveillance (Rao et al., 2016) and also in monitoring the water environment of a river basin (Jing and Tingting, 2015). Underwater sensor network has some unique constraints that are unlike what is encountered in traditional wireless sensor network. For instance, in UWSN propagation of signals is achieved via acoustic communication. Bharamagoudra et al. (2017) have listed some of the issues that arise due to characteristics of acoustic communication, such as low bandwidth, large propagation delay, high energy consumption, channel impairment and high channel error rates. Bahrami et al. (2016) have pointed out that collision avoidance is very difficult in acoustic communication. Karim et al. (2015)