Undersea communication cables (UCCs) are critical for global connectivity but remain vulnerable to physical and cyber threats. This paper presents insights from the NATO Science for Peace and Security Project: Hybrid Space and Submarine Architecture to Ensure Information Security of Telecommunications (HEIST), a system designed to enhance the redundancy and resilience of UCCs. The proposed architecture aims to efficiently reroute data from submarine cables to satellite networks upon detection of threats via enhanced subsea sensing and monitoring. We discuss the components, including secure communication links, real-time situational awareness, and smart contracting for automated routing of compromised UCC communications. We demonstrate the operational capabilities of HEIST in mitigating disruptions through a simulation environment. The architecture indicates improved robustness to accidental or malicious attacks against submarine cables, reinforcing the strategic importance of hybrid multi-domain networks for resilient telecommunications. As such, the HEIST provides a blueprint for a future robust and resilient backbone for the internet.