The rapid expansion of off shore renewable energy including floating wind farms, marine energy converters, and transnational subsea power interconnectors places unprecedented demands on the sealing systems that safeguard these critical assets. Gaskets in submarine cable transition joints, turbine nacelles, underwater connectors, and high-pressure energy storage enclosures are subjected to extreme conditions: high hydrostatic pressure, severe thermal cycling, and large internal volumes that complicate leak detection. The industry-standard pressure decay leak testing method, while simple and cost-effective, is fundamentally compromised by these environmental factors. Temperature fluctuations as small as 1 °C can induce pressure artifacts of several hundred Pascals, masking true leakage or triggering false alarms. Simultaneously, large test volumes common in cable housings and storage vessels exponentially extend detection times, making reliable leak identification impractical. This paper presents a unified mathematical framework that decouples the coupled effects of pressure, temperature, and volume on gasket permeability, enabling accurate leak rate calculation and robust uncertainty estimation. By integrating molecular gas dynamics with poroelastic material theory, the model distinguishes genuine leakage from temperature-induced and volume-induced artifacts. The framework is validated against experimental data across multiple gasket materials, demonstrating predictive accuracy within 12–25% across a wide range of pressure regimes. Practical recommendations are provided for optimizing test parameters, implementing compensation strategies, and designing sealing systems that withstand the harsh marine environment. These findings have direct implications for the reliability of off shore energy infrastructure, reducing the risk of seawater ingress, improving predictive maintenance, and ensuring the long-term integrity of submarine power cables, floating wind turbines, and grid-scale energy storage systems.