Advanced Routing Protocols for Underwater Wireless Sensor Networks: Energy Optimization and Quality of Service Enhancement

Underwater Wireless Sensor Networks (UWSNs) represent a paradigmatic shift in marine exploration and monitoring technologies, enabling unprecedented scientific research and industrial applications in aquatic environments. The unique challenges posed by underwater communication, including severely limited bandwidth, substantial propagation delays, stringent energy constraints, and highly dynamic network topologies, necessitate the development of sophisticated routing protocols specifically tailored for these harsh operating conditions. This comprehensive survey examines the state-of-the-art in advanced routing protocols designed for UWSNs, with particular emphasis on energy optimization strategies and Quality of Service (QoS) enhancement mechanisms. We systematically analyze contemporary routing methodologies spanning fuzzy logic-based decision systems, machine learning approaches, bio-inspired optimization algorithms, and hybrid multi-objective techniques. Through exhaustive examination of research developments from 2018 to 2025, we establish a comprehensive taxonomy of routing strategies, evaluate critical performance metrics, and identify fundamental design principles that govern effective underwater routing protocols. Our analytical findings demonstrate that hybrid approaches integrating fuzzy logic with metaheuristic optimization algorithms consistently achieve superior performance across multiple dimensions, including energy efficiency improvements of 15-40%, packet delivery ratio enhancements of 10-25%, and significant network lifetime extensions. We provide detailed comparative analyses through comprehensive tabular summaries and establish a roadmap for future research directions in next-generation UWSN routing architectures.