Underwater Internet of Things (IoUT) networks have gained considerable attention in recent years due to their wide-ranging applications in exploring and monitoring underwater environments, such as oceans and seas. Compared to previous decades, these networks have significantly improved our ability to understand and interact with aquatic ecosystems. However, several challenges remain, including the dynamic and variable conditions of underwater environments, high propagation delays, and the inherent unreliability of underwater communication channels. Ensuring reliable communication between underwater devices and surface nodes continues to be a critical concern. In this paper, we propose a novel solution that integrates Software-Defined Networking (SDN) architecture with Fog Computing to enhance communication reliability in underwater environments. The proposed method is based on an Integer Linear Programming (ILP) model designed to optimize underwater communication. Specifically, the approach considers communication between traffic-generating underwater nodes and surface-level nodes as a multicast operation. By solving this model, an optimized routing tree is generated that minimizes delays while maximizing reliability. The resulting routing structure is then disseminated to the underwater nodes by the network controller. Simulation results confirm that the adoption of an SDN-Fog-based architecture, combined with multicast routing, significantly enhances underwater communication performance, particularly in terms of reliability and network lifetime.
